Wireless communication device

ABSTRACT

According to one embodiment, a wireless communication device includes a receiver, a controller and a transmitter. The receiver receives a terminal identifier of a first terminal being a target for downlink frequency multiplexing transmission from another wireless communication device, and receives information identifying, of a plurality of frequency components, a first frequency component allocated to the first terminal. The controller selects, of a plurality second terminals belonging to the wireless communication device, a second terminal having a terminal identifier same as that of the first terminal and allocates the first frequency component to the selected second terminal. The transmitter transmits a header at a band including the plurality of frequency components, the header including the terminal identifier of the selected second terminal in a first field corresponding to the first frequency component, and transmits a first frame addressed to the selected second terminal via the first frequency component.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2017-050186, filed on Mar. 15,2017, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate to a wireless communication device.

BACKGROUND

To a cellular system, there has been recently introduced a FractionalFrequency Reuse (FFR) scheme of repeatedly reusing a frequency partiallyto reduce interference with an adjacent base station. In FFR, forexample, a coverage area of the base station is divided into an areanear the base station and an area far from the base station, and thenear area and the far area are allocated with frequency channelsdifferent from each other. The frequency channel used in the area nearthe base station is the same among the adjacent base stations, and thefrequency channel used in the area far from the base station isdifferent between the adjacent base stations. This suppresses decreasein the frequency usage efficiency and improves a throughput of a user.

Concerning the next generation wireless LAN standard, IEEE802.11ax, anAP cooperation technique has been considered as one of differentiationtechnologies for an access point. In IEEE802.11ax, an orthogonalfrequency division multiple access (OFDMA) is introduced, and thus, thefrequency is likely to be efficiently used by applying FFR to wirelessLAN as one of the AP cooperation techniques. However, there has been noconcrete proposal to apply FFR to wireless LAN.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of a wireless communicationsystem according to a first embodiment;

FIG. 2 is a diagram showing a plurality of RUs (resource units) securedin continuous frequency domains of one channel;

FIG. 3 is a diagram showing an allocation pattern of the RU in afrequency bandwidth;

FIG. 4A and FIG. 4B are each a diagram showing an exemplary basic formatof a MAC frame;

FIG. 5 is a diagram illustrating an example in which each of adjacentAPs (access points) 1 and 2 performs DL-OFDMA transmission;

FIG. 6 is a diagram showing an exemplary structure of a physical packetused for DL-OFDMA;

FIG. 7 is a diagram showing an exemplary format of a field forspecifying the RU for each terminal;

FIG. 8 is a diagram showing a situation in which decoding is failedowing to signal collision;

FIG. 9A and FIG. 9B are each a diagram showing an exemplary terminalidentifier assigned to each terminal;

FIG. 10A and FIG. 10B are each a diagram illustrating an example inwhich the adjacent APs set the same value in a field in cooperation witheach other;

FIG. 11A and FIG. 11B are diagrams respectively showing exemplaryphysical packets an AP 1 and an AP 2 transmit by way of DL-OFDMA;

FIG. 12 is a diagram showing an operation sequence of a wireless LANsystem according to the first embodiment;

FIG. 13A is a block diagram of an AP according to the first embodiment;

FIG. 13B is another block diagram of the AP according to the firstembodiment;

FIG. 14 is a block diagram of a terminal according to the firstembodiment;

FIG. 15A is a flowchart of an operation of the AP according to the firstembodiment;

FIG. 15B is a flowchart of another operation of the AP according to thefirst embodiment;

FIG. 16 is a diagram showing an exemplary format of a trigger frame(TF);

FIG. 17 is a diagram showing an exemplary setting for a Virtual AP;

FIG. 18 is a diagram showing an operation sequence of a wireless LANsystem according to a second embodiment;

FIG. 19A and FIG. 19B are diagrams respectively showing exemplaryphysical packets transmitted by way of UL-OFDMA;

FIG. 20A and FIG. 20B are each a diagram showing an example oftransmitting the TF by way of channel-based DL-OFDMA;

FIG. 21 is a diagram showing an exemplary allocation pattern of the RUto a frequency domain;

FIG. 22A and FIG. 22B are each a diagram showing an exemplary setting ina field in a case of DL-MU-MIMO via a particular RU;

FIG. 23 is a diagram showing an operation sequence of a wireless LANsystem according to a third embodiment;

FIG. 24A and FIG. 24B are each a diagram showing an exemplary physicalpacket transmitted by way of DL-OFDMA & MU-MIMO;

FIG. 25 is a functional block diagram of an access point or terminal;

FIG. 26 is a diagram showing an exemplary overall configuration of aterminal or access point;

FIG. 27 is a diagram showing an exemplary hardware configuration of awireless communication device equipped in an access point or terminal;

FIG. 28 is a functional block diagram of a terminal or access point;

FIG. 29A and FIG. 29B are each a perspective view of a terminalaccording to an embodiment of the invention;

FIG. 30 is a diagram showing a memory card according to an embodiment ofthe invention; and

FIG. 31 is a diagram showing an example of frame exchange during acontention period.

DETAILED DESCRIPTION

According to one embodiment, a wireless communication device includes areceiver, a controller and a transmitter. The receiver receives aterminal identifier of a first terminal being a target for downlinkfrequency multiplexing transmission from another wireless communicationdevice, and receives information identifying, of a plurality offrequency components, a first frequency component allocated to the firstterminal. The controller selects, of a plurality second terminalsbelonging to the wireless communication device, a second terminal havinga terminal identifier same as that of the first terminal and allocatesthe first frequency component to the selected second terminal. Thetransmitter transmits a header at a band including the plurality offrequency components, the header including the terminal identifier ofthe selected second terminal in a first field corresponding to the firstfrequency component, and transmits a first frame addressed to theselected second terminal via the first frequency component.

The known wireless LAN standards IEEE Std 802.11™-2012 and IEEE Std802.11ac™-2013, and the next generation wireless LAN standard IEEE802.11-15/0132r17 that is the specification framework document for IEEEStd 802.11ax are entirely incorporated herein by reference.

Hereinafter, a description is given of embodiments of the presentinvention with reference to the drawings.

First Embodiment

FIG. 1 shows a configuration of a wireless communication systemaccording to a first embodiment. This wireless communication systemcomplies with IEEE802.11 standard, but a system complying with anothercommunication scheme than this may be adopted. An AP 1 and an AP 2 arelocated as a plurality of access points (APs). Three or more than APsmay be located.

A basic service set (BSS) 1 is a wireless communication group formed bythe AP 1, to which belong a terminal 11, a terminal 12, a terminal 13, aterminal 14, a terminal 15, and a terminal 16 that are a plurality ofterminals as stations (STAs). In other words, the terminal 11 to theterminal 16 each perform an association process with the AP 1 andcomplete exchange of parameters required for the communication toestablish a wireless link with the AP 1. A state where the terminalestablishes the wireless link with the AP 1 is sometimes referred to asa state where the terminal connects with the AP 1. The AP 1 and theterminal 11 to the terminal 16 are respectively equipped with a wirelesscommunication device. The wireless communication device equipped in theAP 1 communicates with the wireless communications equipped in theterminal 11 to the terminal 16 in compliance with IEEE802.11ax standard.There may exist other terminal than the terminals 11 to 16 in the BSS 1.The relevant terminal may be a terminal complying with IEEE802.11axstandard or a legacy terminal (terminal complying withIEEE802.11b/a/g/n/ac).

Similarly, a basic service set (BSS) 2 is a wireless communication groupformed by the AP 2, to which belong a terminal 21, a terminal 22, aterminal 23, a terminal 27, a terminal 28, and a terminal 29. In otherwords, the terminal 21 to the terminal 23 and the terminal 27 to theterminal 29 each perform the association process with the AP 2 toestablish a wireless link with the AP 2. The AP 2, and the terminals 21to 23 and 27 to 29 are respectively equipped with a wirelesscommunication device. The wireless communication device equipped in theAP 2 communicates with the wireless communications equipped in theterminals 21 to 23 and 27 to 29 in compliance with IEEE802.11 standard.There may exist other terminal than the terminals 21 to 23 and 27 to 29in the BSS 2. The relevant terminal may be a terminal complying withIEEE802.11ax standard or a legacy terminal (terminal complying withIEEE802.11b/a/g/n/ac).

The AP 1 and the AP 2 are connected with each other via a wirelessnetwork or a wired network. The AP 1 and the AP 2 may communicate witheach other in accordance with a scheme complying with IEEE802.11standard or other standards. The AP 1 and the AP 2 may be directlyconnected with each other via a cable to carry out wired communication.In the example in FIG. 1, the AP 1 and the AP 2 are connected with eachother via the wired network.

The terminal 11 to the terminal 13 belong to an area (neighbor area) A1near the AP 1 in a communication area E1 of the AP 1. The terminal 14 tothe terminal 16 belong to an area (distant area) A2 far from the AP 1 inthe communication area E1.

Similarly, the terminal 21 to the terminal 23 belong to an area(neighbor area) B1 near the AP 2 in a communication area E2 of the AP 2.The terminal 27 to the terminal 29 belong to an area (distant area) B2far from the AP 2 in the communication area E2.

The neighbor area A1 is an area where a signal from an adjacent AP (AP2, here) does not reach or a signal strength from the AP 2 is low. Inother words, the neighbor area A1 is an area where the signal from theAP 2 does not interfere with the signal from AP 1 or the interference issmall. In the distant area A2 of the AP 1, there is a part (referred toas an overlap area) overlapping the communication area of the adjacentAP 2, in which a strength of the signal received from the AP 2 is high,and if that signal interferes with the signal from the AP 1, the signalfrom the AP 1 may not be able to be correctly decoded. In the distantarea A2, in other area than the overlap area, there is no or smallinterference with the AP 2, similar to the neighbor area. The neighborarea B1 and distant area B2 of the AP 2 have the same conditions as forthe neighbor area A1 and the distant area A2 concerning the interferencewith the adjacent AP, with only the adjacent AP being exchanged to theAP 1.

In the example shown in the figure, the terminal 11 to the terminal 13exist in the neighbor area A1 of the AP 1, and the terminal 14 to theterminal 16 exist in the distant area A2. The terminal 21 to theterminal 23 exist in the neighbor area B1 of the AP 2, and the terminal27 to the terminal 29 exist in the distant area B2. The terminal 27 andthe terminal 28 of the terminals belonging to the AP 2 exist in theoverlap area.

The AP has the basically same function as the terminal (STA) except forhaving a relay function, and thus, is also one form of the terminal. Inthe example in FIG. 1, the AP 2 is not included in the communicationarea E1 of the AP 1 and the AP 1 is not included in the communicationarea E2 of the AP 2, but in a case where the AP 1 and the AP 2communicate with each other by way of the wireless communicationcomplying with the same standard as the terminal, transmitted power maybe set higher than that of the terminal to perform the communicationbetween the AP 1 and the AP 2.

The AP 1 can perform OFDMA (Orthogonal Frequency Division MultipleAccess) communication that is frequency-multiplexed communication, withone or more terminals selected from the plural terminals 11 to 16. InOFDMA, a resource unit (RU) containing one or more subcarriers isallocated as communication resource to the terminal such that thesimultaneous communications are performed with the plural terminals viathe respective different RUs. Such OFDMA is particularly referred to asRU-based OFDMA. The RU may be also referred to as a sub, a resourceblock, a frequency block, and the like. Uplink OFDMA is designated asUL-OFDMA, and downlink OFDMA is designated as DL-OFDMA. In the presentembodiment, at least the AP 1 is capable of DL-OFDMA.

Similarly, the AP 2 can perform OFDMA (Orthogonal Frequency DivisionMultiple Access) communication with one or more terminals selected fromthe plural terminals 21 to 23 and 27 to 29. In the present embodiment,the AP 2 is capable of at least DL-OFDMA of UL-OFDMA and DL-OFDMA.

FIG. 2 shows resource units (RU #1, RU #2, RU #K) secured in continuousfrequency domains of one channel (designated as a channel M, here). Aplurality of subcarriers orthogonal to each other are arranged in thechannel M, and a plurality of resource units including one or aplurality of continuous subcarriers are defined within the channel M.Although one or more subcarriers (guard subcarriers) may be arrangedbetween the resource units, presence of the guard subcarrier is notessential. The bandwidth of one channel may be for example, though notlimited to these, 20 MHz, 40 MHz, 80 MHz, and 160 MHz. One channel maybe constituted by combining a plurality of channels of 20 MHz. OFDMAcommunication is realized by different resource units beingsimultaneously used by different terminals.

The number of the subcarriers (tones) contained in one resource unit maybe different for each resource unit. For example, the number of thesubcarriers (tones) in one RU may be variously 26, 52, 106, and 242.

FIG. 3 shows an allocation pattern of the RU in a certain frequencybandwidth BW (20 MHz, here). For example, 26 patterns may be adopted.Assume that 26 subcarriers are included in the RU arranged at the centerof the frequency bandwidth. A numeral on the left side of each patternin the figure represents an allocation pattern number. A numeral in eachrectangle represents the number of the subcarriers.

FIG. 4A shows an exemplary basic format of a MAC frame. The MAC frameaccording to the present embodiment is based on such a frame format.This frame format contains fields of a MAC header, a Frame body, and anFCS. The MAC header contains fields of a Frame Control, a Duration/ID,an Address 1, an Address 2, an Address 3, a Sequence Control, a QoSControl, and an HT (High Throughput) control as shown in FIG. 4B.

These fields do not need to always exist and there may be cases wheresome of these fields do not exist. The field of Address 3 may not existin some cases, for example. Also, there may be other cases where both oreither one of the QoS Control field and the HT Control field does notexist. Also, there may be still other cases where the frame body fielddoes not exist. Also, any field or fields that are not illustrated inFIG. 4B may exist. For example, an Address 4 field may further exist.

The field of Address 1 indicates Receiver Address (RA), the field ofAddress 2 indicates Transmitter Address (TA), and the field of Address 3indicates either BSSID (Basic Service Set IDentifier) (which may be thewildcard BSSID whose bits are all set to 1 to cover all of the BSSIDsdepending on the cases) which is the identifier of the BSS, or TA,depending on the purpose of the frame.

Two fields of Type and Subtype or the like are set in the Frame Controlfield. The rough classification of the MAC frame as to whether it is thedata frame, the management frame, or the control frame is made by theType field, and more specific types, for example, fine discriminationamong the roughly classified frames is made by the Subtype field. Atrigger frame described later may be also classified by the Type and theSubtype in combination with each other.

The Duration/ID field describes the medium reserve time, and it isdetermined that the medium is virtually in the busy state from the endof the physical packet containing this MAC frame to the medium reservetime when a MAC frame addressed to another terminal is received. Thescheme of this type to virtually determine that the medium is in thebusy state, or the period during which the medium is virtually regardedas being in the busy state, is, as described above, called NAV (NetworkAllocation Vector). The Sequence control field stores therein a sequencenumber of a frame or the like. The QoS control field is used to carryout QoS control to carry out transmission with the priorities of theframes taken into account. The HT Control field is a field introduced inIEEE802.11n.

In the management frame, an information element (IE) to which a uniqueElement ID (IDentifier) is assigned is set in the Frame Body field.

One or a plurality of information elements may be set in the Frame Bodyfield.

Frame check sequence (FCS) information is set in the FCS field as achecksum code for use in error detection of the frame on the receptionside. As an example of the FCS information, CRC (Cyclic Redundancy Code)may be mentioned.

A description is given of the technical challenge to be solved by thepresent embodiment with reference to FIG. 5. FIG. 5 shows an example inwhich the AP 1 performs DL-OFDMA communication with the terminals 11 to16, and the AP 2 performs DL-OFDMA communication with the terminals 21to 23 and 27 to 29. Assume that both the AP 1 and the AP 2 use a channel1 (Ch1) as the same frequency band. The AP 1 allocates the resourceunits (RUs) 1 to 6 to the terminals 11 to 16, respectively. The AP 2allocates the RU 1 to the RU 3 and the RU 7 to the RU 9 to the terminals21 to 23 and 27 to 29, respectively. A bandwidth of the channel may bevariously 20 MHz, 40 MHz, 80 MHz, and 160 MHz, and here assume 20 MHz.The channel 1 includes the RUs 1 to 9.

An exemplary operation of DL-OFDMA transmission from the AP 1 to theterminals 11 to 16 is described. FIG. 6 shows an exemplary structure ofa physical packet used for DL-OFDMA. Assume a situation where the AP 1transmits by way of DL-OFDMA the MAC frames (MAC frames 11 to 16) to theterminals 11 to 16, respectively. The AP 1 transmits a physical packetcontaining a legacy field, the SIG 1 field, and the MAC framestransmitted via the RU for each of the terminals 11 to 16. In otherwords, the common SIG 1 field is added to the MAC frames 11 to 16addressed to the terminals 11 to 16. Then, the legacy field defined byIEEE802.11 standard is added to a head of the SIG 1 field to configurethe physical packet. Therefore, in the physical packet for the terminals11 to 16, the legacy field and the SIG 1 field are common to theterminals 11 to 16 and the MAC frames are individually set for therespective terminals. Another field (e.g., SIG 2 field, STF (ShortTraining Field), LTF (Long Training Field) and the like) may be providedfor each RU between the SIG 1 field and the MAC frames.

The legacy field includes an L-STF (Legacy-Short Training Field), anL-LTF (Legacy-Long Training Field), and an L-SIG (Legacy Signal Field).The L-STF, the L-LTF, and the L-SIG, which are each a field capable ofbeing recognized by a terminal of the legacy standard such asIEEE802.11a, for example, have stored therein information such as onsignal detection, frequency correction (channel estimation), andtransmission speed.

Control information notified to the terminals 11 to 16 is set in the SIG1 field. As an example of the control information, set is informationspecifying the RU for each of the terminals 11 to 16 (RU 1 to RU 6,here). Concretely, the information is set with a terminal identifier ofthe terminal (also designated as STAID in some cases) being associatedwith the RU to be used. The terminal identifier (STAID) may be anAssociation ID (AID) assigned from the AP 1 in the association process,a part of the AID (Partial AID), or another identifier such as a MACaddress. In the SIG 1 field, information required for decoding the MACframe such as MCS (Modulation And Coding Scheme), or other informationmay be set for each of the RUs specified to the terminals 11 to 16. TheSIG 1 field includes a PHY HE-SIG-A field and an HE-SIG-B fieldinvestigated in IEEE802.11ax as an example.

FIG. 7 shows an exemplary format of a field for specifying the RU foreach terminal in the SIG 1 field. The field shown in the figure containsan RU allocation Sub-field and a User specific field which is defined inthe PHY HE-SIG-B field investigated in IEEE802.11ax. The RU allocationSub-field is set to a value indicating a RU allocation pattern. Forexample, a value “00000000” means the allocation patterns of nine RUs (9multiplex allocation) with one RU including 26 subcarriers. Nine RUs areassigned with numbers (#1 to #9) in accordance with a predeterminedrule. These RUs are represented as an RU #1 to an RU #9. The Userspecific field includes a User field #1 to a User field #9. The numberof the User fields is variable and, here, corresponds to a case where avalue of the RU allocation Sub-field is “00000000” (9 multiplexallocation) described above. The User field #1 to the User field #9 arerespectively associated with the RU #1 to the RU #9, and arerespectively set to information (terminal allocation information) on theterminals allocated with the RU #1 to the RU #9. For example, the Userfield may be set to the terminal identifier (STAID). Besides the STAID,it may be set to the information such as the MCS.

For example, a case where the User field #1 set to STA1 and MCS3 meansthe RU #1 is allocated to a terminal having STA1 and a MAC frametransmitted via the RU #1 is decoded by the MCS identified from MCS3.The following description assumes a case where the SIG 1 field containsthe field in FIG. 7. However, a format for allocating the RU for eachterminal is not limited to that in FIG. 7, and another format may beadopted.

If another field (e.g., the SIG 2 field) is provided for each RU betweenthe SIG 1 field and the MAC frames, the MCS required for decoding theMAC frame may be configured to be set not in the SIG 1 field but in theSIG 2 field.

The AP 1 transmits the legacy field and the SIG 1 field at the channelwidth band (20 MHz) to transmit, for each RU specified in the SIG 1field, the MAC frame addressed to the terminal allocated with the RU.

The terminals 11 to 16 receiving the signal from the AP 1 process thelegacy field before decoding the SIG 1 field to identify the RU whichthe terminal itself is to decode. For example, each terminal confirms avalue of the RU allocation Sub-field in FIG. 7 to identify the RUallocation pattern. Here, the value of the RU allocation Sub-field of“00000000” (9 multiplex allocation) is confirmed. Each terminal checkswhether or not the User field in which the STAID of the terminal itselfis set exists among the User field #1 to the User field #9. If theterminal detects the User field in which the STAID of the terminalitself is set, the terminal confirms that the terminal itself isallocated with a signal of the RU associated with the number of the Userfield. For example, if the terminal 13 detects that the User field #3 isset to the STAID of the terminal 13 itself, the terminal 13 confirmsthat the RU #3 is allocated to itself. The terminal also detectsinformation (MCS or the like) other than the STAID from the User fieldin which the STAID of the terminal itself is detected. Each terminaldecodes the signal of the RU allocated to the terminal itself using thedetected MCS to decode the subsequent payload so as to receive the MACframe addressed to the terminal itself. In the example, in this way, theterminals 11 to 16 receive the MAC frames 11 to 16 addressed to theterminals themselves via the RU #1 to the RU #6, respectively. Theterminals 11 to 16 carry out a check (CRC check or the like) on thebasis of the FCS in the MAC frame, and if a check result is a success,they transmit an acknowledgement response frame (e.g., ACK frame, BA(Block Ack) frame, or the like) to the AP 1, as needed. The ACK frame istransmitted by, for example, a carrier sense on the basis of CSMA/CA toacquire an access right with respect to the wireless medium.

Similarly, the AP 2 also transmits by way of DL-OFDMA the MAC frames(MAC frames 21 to 23 and 27 to 29) to the terminals 21 to 23 and 27 to29, respectively. Concretely, the AP 2 transmits a physical packetcontaining the legacy field, the SIG 1 field, and a plurality of MACfields addressed to the terminals 21 to 23 and 27 to 29. In the SIG 1field, set is information specifying the RUs (the RU 1 to the RU 3 andthe RU 7 to the RU 9, here) allocated to the terminals 21 to 23 and 27to 29 or the like using the format in FIG. 7. The terminals 21 to 23 and27 to 29 receiving the signals downlink-transmitted from the AP 2respectively identify the RUs allocated to the terminals themselves fromthe SIG 1 fields in a manner similar to the terminals 11 to 16. Then,the terminals respectively decode the payloads transmitted via therelevant RUs to receive the MAC frames 21 to 23, 27 to 29 addressed tothe terminals themselves.

Here, because the AP 1 and the AP 2 use the same channel (Ch1), theterminals 27 and 28, for example, in the overlap area receive thesignals from both APs and fail to decode the signals owing to signalcollision in some cases, if the AP 2 performs the DL-OFDMA transmissionwhen the AP 1 performs DL-OFDMA transmission, or if the AP 1 and the AP2 simultaneously perform DL-OFDMA transmission. FIG. 8 shows thissituation. The example shows an exemplary operation focusing on theterminal 16 and the terminal 28. The characters “TX” and “RX” mean thetransmission and the reception, respectively.

The AP 1 transmits by way of DL-OFDMA a physical packet (S1), and theterminal 16 receives the physical packet. The terminal 16 succeeds inreceiving the MAC frame addressed to the terminal 16 itself andtransmits an ACK frame (S2). The signal transmitted by the AP 1 is alsoreceived by the terminal 28 in the overlap area. The terminal 28, whilereceiving the signal from the AP 1, also receives the physical packetsignal transmitted by way of DL-OFDMA transmission from the AP 2 (S3),which is dealt with as a reception error, and then fails to decode thephysical packet (fails to decode the header or the like). Here, theterminal 28 is focused on, but a similar situation occurs in theterminal 27. The terminals 21 to 23 and 29, which the signal from the AP1 does not reach, succeed in receiving the physical packet transmittedfrom the AP 2. The terminals 11 to 15 belonging to the BSS 1, which thesignal from the AP 2 also does not reach, succeed in receiving thephysical packet transmitted from the AP 1. In this way, in the casewhere the AP 1 and the AP 2 adjacent to each other use the same channel,the terminal the signal from the adjacent AP does not reach succeeds inreceiving the physical packet transmitted by way of DL-OFDMAtransmission from the AP in the BSS of itself, but the terminal thesignal from the adjacent AP reaches is likely to fail to receive thephysical packet transmitted by way of DL-OFDMA transmission from the APin the BSS of itself owing to the signal collision. This leads todecrease in frequency usage efficiency.

In the present embodiment, the AP 1 and the AP 2 communicate with eachother to cooperatively operate to improve the frequency usageefficiency. Concretely, the AP 1 and the AP 2 select the terminalshaving the same STAID as a terminal allocated with the same RU, and setthe terminal allocation information of the selected terminal in the Userfield corresponding to the relevant RU. Each of the AP 1 and the AP 2selects a terminal having an arbitrary STAID for the RU not used by apartner AP (the AP 2 with respect to the AP 1, or the AP 1 with respectto the AP 2), and sets the terminal allocation information of theselected terminal in the User field corresponding to the relevant RU.For the RU used by the partner AP, the terminal allocation informationis acquired from the partner AP, and the acquired terminal allocationinformation is set in the User field corresponding to the relevant RU.On the basis of such a setting, values of the RU Allocation Sub-fieldsand User specific fields generated by the AP 1 and the AP 2 are the samevalues. Each of the AP 1 and the AP 2 generates the SIG 1 fieldcontaining the RU Allocation Sub-field and the User specific field. Notethat values of another field in the SIG 1 field are identical betweenthe AP 1 and the AP 2 in accordance with a predefinition or a previouscooperation. Then, each of the AP 1 and the AP 2 transmits the legacyfield and the SIG 1 field at the channel width band, and transmits theMAC frame via the RU which the terminal itself allocates to theterminal. Each AP does not transmit the frame via RU which the terminalitself does not allocate to the terminal. The transmissions from the AP1 and the AP 2 are simultaneously performed. The terminal receiving thesignals from both the AP 1 and the AP 2 (e.g., the terminal in theoverlap area, such as the terminals 28 and 27) receives the signals fromthe AP 1 and the AP 2 at the same time. Even if such a terminal receivesthe signals simultaneously transmitted from the AP 1 and the AP 2, sincethe values common to the AP 1 and the AP 2 are set in the legacy fieldsand the SIG 1 fields, the terminal can decode these fields. Therefore,the terminal can identify the RU allocated to the terminal itself from aresult of decoding the SIG 1 field to receive the MAC frame transmittedvia the identified RU. This allows DL-OFDMA transmission also to theterminal in the overlap area to be succeeded, improving the frequencyusage efficiency.

Hereinafter, a specific example of this scheme is shown. As shown inFIG. 9A, assume that the AP 1 assigns an ID 1 to an ID 6 as the STAIDsto the STA 11 the STA 16. Assume that the AP 2 assigns the ID 1 to theID 3 and an ID 7 to an ID 9 as the STAIDs to the STA 21 to the STA 23and the STA 27 to the STA 29 as shown in FIG. 9B. The STAIDs of the STA11 to the STA 13 are the same as the STAIDs of the STA 21 to the STA 23,respectively. In this case, consider a situation where the AP 1 and theAP 2 allocate the RUs to the terminals relating to themselves, andperform DL-OFDMA transmissions respectively to the STA 11 to the STA 16,and the STA 21 to the STA 23 and the STA 27 to the STA 29 as describedin FIG. 5.

FIG. 10A shows an exemplary setting of the User field #1 to the Userfield #9 in the AP 1. FIG. 10B shows an exemplary setting of the Userfield #1 to the User field #9 in the AP 2.

Assume that both the AP 1 and the AP 2 use the same RUs (the RU #1 to RU#3, here) in the respective neighbor areas. Each of the AP 1 and the AP2 sets the same STAIDs in the User Fields regarding these RUs. The AP 1sets the ID 1 to the ID 3 (that is, the STAIDs of the terminal 11 to theterminal 13) in the User field #1 to the User field #3. The AP 2 setsthe ID 1 to the ID 3 (that is, the STAIDs of the terminal 21 to theterminal 23) in the User field #1 to the User field #3.

On the other hand, both the AP 1 and the AP 2 allocate, as for the RUsused in the respective distant areas (the RU #4 to the RU #9, here), theRU not used by the partner AP to the terminal. In the example, the AP 1sets the ID 4 to the ID 6 (that is, the STAIDs of the terminal 14 to theterminal 16) in the User field #4 to the User field #6. The AP 2determines that the RU #4 to the RU #6 cannot be used because being usedby the AP 1, but the RU #7 to the RU #9 are not used by the AP 1, andthen, sets the ID 7 to the ID 9 (that is, the STAIDs of the terminal 27to the terminal 29) in the User field #7 to the User field #9.

For the RU used by only the partner AP, both the AP 1 and the AP 2acquire the terminal allocation information set for the relevant RU(here, assuming only the STAID for ease of description) from the partnerAP, and set the acquired terminal allocation information in the Userfield corresponding to the relevant RU. In the example, the AP 1 setsthe ID 7 to the ID 9 (that is, the STAIDs of the terminal 27 to theterminal 29) acquired from the AP 2 in the User field #7 to the Userfield #9. The AP 2 sets the ID 4 to the ID 6 (that is, the STAIDs of theterminal 14 to the terminal 16) acquired from the AP 1 in the User field#4 to the User field #6. This allows the values of the RU AllocationSub-field and User specific field generated by the AP 1 and the AP 2 tobe the same. In the RU allocation Sub-field, the same value between theAP 1 and the AP 2 is set.

In the User field, the STAID only is set as the terminal allocationinformation here, but other information such as the MCS may be set. Inthis case also, the AP 1 and the AP 2 cooperate with each other suchthat the same values between the AP 1 and the AP 2 are set in all of theUser field #1 to the User field #9.

The AP 1 and the AP 2 transmit the same legacy fields and the same SIG 1fields at the channel width band, and subsequently, each of themtransmits, via the RU specified by itself to the terminal belonging toitself in the SIG 1 field, the relevant MAC frame addressed to theterminal.

FIG. 11A shows an exemplary physical packet the AP 1 transmits. Anabscissa represents a time, and an ordinate represents a frequency.Here, the frequency increases in order from the RU #1 to the RU #9, butis not limited thereto. The legacy field and the SIG 1 field aretransmitted at the channel width band (20 MHz), and the MAC frame istransmitted via the corresponding RU. If the above described anotherfield is provided between the SIG 1 field and the MAC frame, therelevant field is also transmitted via the same RU as for the MAC frame.The RU not allocated with the terminal (the RU #7 to the RU #9) is notused for the transmission of the MAC frame. The characters “STA11” to“STA16” in the figure mean that the MAC frames are addressed to theterminals 11 to 16. FIG. 11B shows an exemplary physical packet the AP 2transmits. In the AP 2, since the RU #4 to the RU #6 are not allocatedto the terminals, the MAC frame is not transmitted via these RUs.

The terminal in the overlap area (assume the terminal 28, for example)receives the signals from both the AP 1 and the AP 2 at the same time.The legacy field and the SIG 1 field transmitted from the AP 1 and thelegacy field and the SIG 1 field transmitted from the AP 2 are the samein the signals. Therefore, the terminal 28 can normally decode thelegacy field and the SIG 1 field to detect the RU allocation Sub-fieldand the User specific field (see FIG. 10B). The terminal 28 detects theSTAID (=ID 8) of the terminal 28 itself from the User field #8.Therefore, the terminal 28 can decode the signal transmitted via the RU#8 to receive the MAC field addressed to the terminal 28 itself. The MACframe is not transmitted via the RU #7 to the RU #9 from the AP 1 suchthat the signal collision does not occur in the RU #8 via which theterminal 28 receives the signal.

As described above, the AP 1 and the AP 2 cooperate with each other toallocate the same RU used by both APs to the terminals having the sameSTAID and coordinate the information set in physical header parts (SIG 1fields or the like) to be identical between the AP 1 and the AP 2 suchthat even if the AP 1 and the AP 2 use the same channel to performOFDMA, the high frequency usage efficiency can be obtained. In otherwords, FFR for using the same RU by a plurality of APs at the same timecan be achieved in a wireless LAN system.

FIG. 12 shows an exemplary operation sequence of a wireless LAN systemaccording to the present embodiment. Once the AP 1 determines tocooperate with the AP 2 to perform DL-OFDMA transmission (a part of theRUs are used by both APs in common to perform DL-OFDMA transmission), ittransmits data including information required for the cooperation(hereinafter, sometimes referred to as FFR information) to the AP 2(S11).

More specifically, the AP 1 determines the RU allocation pattern to beused. Here, the 9 multiplex pattern described above is selected. On thebasis of the number of the terminals in the neighbor area A1 or thelike, the RU to be used in common with the AP 2 (the RU turned on an FFRfunction: RU for FFR) is determined. Here, the determination is madethat the terminals 11 to 13 exist in the neighbor area A1 and the datato be transmitted to these terminals exists, and three RUs (the RU #1 tothe RU #3, here) are determined as the RU for FFR. The AP 1 determinesthat the data to be transmitted to the terminals 14 to 16 in the distantarea A2 exists, and determines the RU #4 to the RU #6 as the RUsallocated to these terminals. The AP 1 transmits, as FFR information tobe transmitted to the AP 2, a value indicating the RU allocationpattern, information (FFR-on information) specifying the RU for FFR (theRU #1 to the RU #3), and information (FFR correspondence information)specifying the terminal allocation information associated with the RU(the RU #1 to the RU #6). The terminal allocation information includesat least STAID, and may include the MCS and other information. Here, theFFR-on information includes the identifiers of the RU #1 to the RU #3.The FFR correspondence information includes information associating theidentifiers of the RU #1 to the RU #6 with the terminal allocationinformation of the terminal 11 to the terminal 16 (the ID 1 to the ID 6or the like).

Note that the RU allocation pattern and the RU for FFR are determined bythe AP 1 here, but, as another method, may be determined throughnegotiation between the AP 1 and the AP 2 in advance, or determined bythe system or in a specification in advance.

The AP 2 grasps the RU for FFR on the basis of the FFR-on informationincluded in the FFR information received from the AP 1. Here, the AP 2grasps that the RU #1 to the RU #3 are the RUs for FFR. The AP 2allocates the RU #1 to the RU #3 to the terminals having the STAIDs (theID 1 to the ID 3) on the basis of the FFR correspondence information,similarly to the AP 1. Here, the RU #1 to the RU #3 are respectivelyallocated to the STA 21 to the STA 23 having the ID 1 to the ID 3 as theSTAIDs. The AP 2 determines that the AP 1 does not use the RU #7 to theRU #9, and allocates the RU #7 to the RU #9 respectively to the STA 27to the STA 29 having the ID 7 to the ID 9 as the STAIDs. The AP 2transmits as the FFR information, to the AP 1, the terminal allocationinformation of the terminal allocated with the RU not used by the AP 1and the identifier of the RU (S13). Here, transmitted is informationassociating the identifiers of the RU #7 to the RU #9 with the terminalallocation information of the terminal 27 to the terminal 29 (the ID 7to the ID 9 or the like).

The AP 1 receiving the FFR information from the AP 2 determinesexecution timing for DL-OFDMA and transmits a DL-MU (DownlinkMulti-User) notification frame including execution timing information tothe AP 2 (S14). The execution timing for DL-OFDMA may be set inaccordance with a time, or a time lapse from a head to an end a DL-MUstart notification frame. One of a plurality of predetermined timingcandidates may be specified. The execution timing may be specified byother methods than those mentioned here.

When the execution timing for DL-OFDMA arrives, the AP 1 and the AP 2perform DL-OFDMA transmission (S15, S16). This allows the AP 1 and theAP 2 to simultaneously perform DL-OFDMA transmission. The AP 1 transmitsthe physical packet shown in FIG. 11A, and the AP 2 transmits thephysical packet shown in FIG. 11B. Here, the values of the RU allocationSub-fields and User specific fields in the physical packets transmittedby the AP 1 and the AP 2 are the same. Values of other fields in the SIG1 field than these fields are identical between the AP 1 and the AP 2.The legacy fields are also identical between the AP 1 and the AP 2.

Each of the terminals 21 to 23 and 27 to 29 specified in the SIG 1 fieldin the physical packet transmitted by the AP 2 interprets the SIG 1field, identifies the RU allocated to the terminal itself, and decodesthe signal of the identified RU to receive the MAC frame. Particularly,the terminal 27 and the terminal 28 simultaneously receive the signalsof the physical packets from both the AP 1 and the AP 2, but since thevalues of the SIG 1 fields are the same, the received signals can becorrectly decoded (S18). The figure, focusing on the terminal 28, showsthe situation where the terminal 28 succeeds in the reception, but theterminal 27, the terminals 21 to 23, and 29 can also correctly decodethe received signals. Each of the terminals 11 to 16 specified in thephysical packet transmitted by the AP 1 interprets the SIG 1 field,identifies the RU allocated to the terminal itself, and decodes thesignal of the identified RU to receive the MAC frame (S17). The figure,focusing on the terminal 16, shows the situation where the terminal 16succeeds in the reception, but the same holds for the terminals 11 to15.

In the above exemplary sequence, a part of the RU #1 to the RU #9 isused as the RU for FFR, but all of the RU #1 to the RU #9 may be used asthe RUs for FFR. A plurality of RUs for FFR may be also allocated to oneterminal. Both the RU for FFR and RUs other than the RU for FFR(referred to as a usual RU) may be allocated to one terminal.

The AP 2 transmits, at step 13 in FIG. 12, the FFR information includingthe terminal allocation information of the terminal allocated with theRU (usual RU) other than the RU for FFR and the like, but if the AP 2does not allocate the usual RU to the terminal, the transmission of theFFR information may be omitted. In this case, if the AP 1 does notreceive the FFR information from the AP 2 even after elapse of a certaintime period from transmitting the FFR information from the AP 1 itself,it may determine that the AP 2 does not allocate the usual RU to theterminal and transmit the DL-MU start notification frame.

If the AP 2 wants to use an RU as an RU for FFR different from the RUfor FFR determined by the AP 1, the AP 2 may transmit a frame requestingto redetermine the RU for FFR to the AP 1. In this case, the AP 2 mayspecify the RU for FFR the AP 2 wants to use in the relevant frame. Ifthe AP 1 receives the relevant frame, it redetermines the RU for FFR andperforms again the sequence similar to that in FIG. 12.

FIG. 13A is a functional block diagram of the wireless communicationdevice equipped in the AP 1 or the AP 2 (hereinafter, referred to as theAP). The AP performs the wireless communication with the terminal in theBSS formed by the AP. Here, a configuration is shown in a case where theAP communicates with the adjacent AP using the same communication schemeas the terminal.

The wireless communication device in the AP includes a controller 101, atransmitter 102, a receiver 103, antennas 12A, 12B, 12C and 12D, and abuffer 104. The number of the antennas is four here although at leastone antenna may be provided. The controller 101 corresponds tocontrolling circuitry or a baseband integrated circuitry which controlscommunication with the terminals, and the transmitter 102 and thereceiver 103 form a wireless communicator or an RF integrated circuitrywhich transmits and receives frames via the antenna as an example. Aprocess of the controller 101, and all or a part of a digital regionprocess of the transmitter 102 and the receiver 103 may be performed bysoftware (program) executing on a processor such as a CPU, or may beperformed by hardware, or may be performed by the both of software andhardware. The AP may include a processor performing the process of thecontroller 101, all or a part of the transmitter 102 and the receiver103.

The buffer 104 is a storage for transferring a frame and the likebetween an upper layer and the controller 101. The buffer 104 may be avolatile memory such as a DRAM or a non-volatile memory such as a NAND,or an MRAM. The upper layer stores the frame received from anothernetwork in the buffer 104 for relaying to the network in the terminalside belonging to the BSS of itself. The upper layer may take in, fromthe controller 101, the frame received from the terminal side or apayload thereof via the buffer 104. The upper layer may perform an uppercommunication process than a MAC layer such as a TCP/IP or a UDP/IP.Alternatively, the TCP/IP or the UDP/IP may be performed in thecontroller 101 and the upper layer may also perform a process of anapplication layer of processing the data upper than the TCP/IP or theUDP/IP.

An operation of the upper layer may be performed by software (program)processing by a processor such as a CPU, or may be performed byhardware, or may be performed by the both of the software and thehardware. The controller 101 mainly performs a process of the MAC layer,and a part of a process of a physical layer (e.g., a process concerningOFDMA or the like). The controller 101 transmits and receives the framevia the transmitter 102 and the receiver 103 to control thecommunication with the terminals. The controller 101 communicates withthe adjacent AP via the transmitter 102 and the receiver 103 to exchangeinformation (FFR information) required for cooperation of multiusertransmission such as the DL-OFDMA. The controller 101 periodicallytransmits a beacon frame for notifying attribute information,synchronization information and the like of the BSS (Basic Service Set)of the AP. The controller 101 may include a clock generator generating aclock to manage an internal time using the clock generated by the clockgenerator. The controller 101 may output externally the clock created bythe clock generator. Alternatively, the controller 101 may receive aclock generated by an external clock generator to manage an internaltime using the relevant clock generated.

The controller 101, on receiving an association request from theterminal, performs an association process to exchange requiredinformation on capability or an attribute etc. each other andestablishes the wireless link with the terminal. The capabilityinformation may include information of whether to be capable ofDL-OFDMA. The capability information may include information of the RUallocation pattern capable for the terminal, information of the usableRU, and the like. The controller 101 may perform a process such as anauthentication process with the terminal if necessary before receivingthe association request. The controller 101 periodically checks thebuffer 104 to confirm the state of the buffer 104. Alternatively, thecontroller 101 may check the state of the buffer 104 according to atrigger given from an external device.

The transmitter 102 adds a physical header to a frame to be transmittedto generate a physical packet, and further performs processes of thephysical layer such as coding and modulation process. The transmitter102 subjects the physical packet after being modulated to DA conversion,a filtering process to extract components of a desired band, frequencyconversion (up-conversion) and the like to amplify signals obtainedthrough these processes by a pre-amplifier and radiate the amplifiedsignals as radio waves from one or more antennas into the space. Thetransmitter 102 may acquire from the controller 101 information requiredfor generating a part or all of the physical header. A part or all ofthe physical header may be added by the controller 101. An exemplaryoperation in the case of OFDMA transmission is described later.

The signal received by each antenna is, in the receiver 103, amplifiedby a low noise amplifier (LNA), subjected to frequency conversion(down-convert), and subjected to a filtering process, thereby allowing adesired band component to be extracted.

The extracted signal is further converted into digital signals throughAD conversion and subjected to the processes of the physical layer suchas demodulation, error-correcting decode, and a process of the physicalheader, and thereafter, the frame is input to the controller 101. A partor all of the processes of the physical header may be performed by thecontroller 101. Note that in the case of UL-OFDMA as in anotherembodiment described later, the signals transmitted from the respectiveplural terminals are separated for each RU to extract a frame (dataframe, ACK frame, or the like) for each terminal.

If the controller 101 receives a frame requiring an acknowledgementresponse, on the basis of a check result of the received frame, itgenerates an acknowledgement response frame (ACK frame, BA frame, or thelike) and transmits the generated acknowledgement response frame via thetransmitter 102. In a case where the frames are transmitted from aplurality of terminals by way of UL-OFDMA described later, thecontroller 101 may transmit, as the acknowledgement response frame, aMulti-Station BA frame investigated in IEEE802.11ax.

As a first exemplary operation of the AP according to the presentembodiment (corresponding to the exemplary operation of the AP 1 in FIG.12), the controller 101 determines to perform DL-OFDMA at an arbitrarytiming. The controller 101 determines the RU allocation pattern (seeFIG. 3), and determines the RU for FFR from among a plurality of RUsincluded in the determined RU allocation pattern. One or more terminalsas targets to which DL-OFDMA is to be performed are selected from amongterminals (terminals compliant with OFDMA) establishing the wirelesslink. The controller 101 allocates an RU (RU for FFR or other RU (usualRU)) to the selected terminal. The RU for FFR and the usual RU areallocated here, but only the RU for FFR may be allocated. The selectionof the terminal precedes the allocation here, but the RU (RU for FFR,usual RU) may be selected first, and then, the terminal allocated withthe RU may be selected.

As an example, the terminal allocated with the RU for FFR is a terminalin the neighbor area, and the terminal allocated with the usual RU is aterminal in the distant area. Which is the terminal belongs to may bedetermined by any method. For example, the determination may be made bycomparing received power from the terminal with a threshold.Alternatively, in a case where the AP is equipped with a GPS (GlobalPositioning System), it may determine utilizing the GPS. The controller101 may estimate a distance from the terminal to make the determinationon the basis of the estimated distance. However, the RU for FFR may beallocated to a terminal in the distant area (for example, a terminalexisting on an opposite side of the adjacent AP and not belonging to theoverlap area). The usual RU may be also allocated to a terminal in theneighbor area.

The controller 101 determines the MCS, a packet length (PPDU length orthe like), and other parameters with respect to the selected terminalsas needed.

The controller 101 transmits the FFR information to the cooperativepartner AP via the transmitter 102. The FFR information includes, forexample, the FFR-on information (information specifying the RU for FFR),the FFR correspondence information (information associating theidentifier of the RU (RU for FFR and usual RU) with the terminalallocation information (STAID or the like) of the terminal allocatedwith the relevant RU), and the value of the RU allocation pattern.

Once the controller 101 receives the FFR information from the partnerAP, it determines execution timing for DL-OFDMA and transmits the DL-MUstart notification specifying the execution timing. When the executiontiming (predetermined timing) specified in the DL-MU start notificationarrives, the controller 101 performs DL-OFDMA. Concretely, thecontroller 101 sets the terminal allocation information (terminalidentifier or the like) of each terminal selected above in a field (Usefield) regarding the RU allocated to the relevant terminal. On the basisof the FFR information received from the partner AP, the controller 101sets the terminal allocation information of the terminal allocated withthe usual RU which is used by the partner AP in a field (User field)regarding the relevant usual RU. In the RU allocation Sub-field, thevalue of the RU allocation pattern is set. In other fields also, values(common to the AP 2) are set to generate the SIG 1 field. The controller101 transmits the physical packet containing the legacy field, the SIG 1field, and the MAC frames addressed to the terminals selected above.More specifically, the controller 101 transmits the header containingthe legacy field and the SIG 1 field using at the channel width band,and transmits the MAC frames, subsequent to the header, addressed to theselected terminals via the RUs allocated respectively to the terminals.Of a plurality of RUs included in the channel width band, the RUallocated to no terminal by the controller 101 is not used for thetransmission.

The RU allocation Sub-field is used to associate the User fields withthe RUs here, but the User fields may be directly set to the identifiersof the RUs as a method. This also allows to grasp the correspondencebetween the terminal and the RU. In this case, with the cooperation ofthe AP and the partner AP, the identifier of which RU is set (or, whichterminal identifier is set) in which position of the User fields may bedetermined through negotiation between both APs, or a rule for thesetting therefor may be defined in advance.

As a second exemplary operation of the AP according to the presentembodiment (corresponding to the exemplary operation of the AP 2 in FIG.12), once the controller 101 receives the FFR information from thepartner AP, it determines to perform DL-OFDMA. The controller 101 graspsthe RU allocation pattern and the RU for FFR on the basis of the FFRinformation. The AP selects, as the terminal allocated with the RU forFFR, from among the terminals (terminals compliant with OFDMA)establishing the wireless link, a terminal having a terminal identifierthe same as the terminal identifier of the terminal to which the partnerAP allocates the same RU for FFR. The AP selects the terminal allocatedwith the RU not used by the partner AP of the usual RUs as needed. Thecontroller 101 allocates the RU (RU for FFR or usual RU) to each of theselected terminals. There are the terminal allocated with the RU for FFRand the terminal allocated with the usual RU here, but there may be onlythe terminal allocated with the RU for FFR. The controller 101determines the MCS, a packet length (PPDU length or the like), and otherparameters with respect to the selected terminals as needed. In thiscase, with respect to the terminal allocated with the RU for FFR,determined are values the same as those for the terminal to which thepartner AP allocates the relevant RU for FFR. The controller 101transmits the FFR information to the cooperative partner AP via thetransmitter 102. The FFR information includes information associatingthe identifier of the usual RU with the terminal allocation information(STAID or the like) of the terminal allocated with the usual RU.

Once the controller 101 receives the DL-MU start notification from thepartner AP, it performs DL-OFDMA when the execution timing specified bythe DL-MU start notification (predetermined timing) arrives. Concretely,the controller 101 sets the terminal allocation information (terminalidentifier or the like) of each terminal selected above in a field (Usefield) regarding the RU allocated to the terminal. On the basis of theFFR information received from the partner AP, the controller 101 setsthe terminal allocation information of the terminal allocated with theRU (usual RU) which is used by the partner AP in a field (User field)regarding the relevant usual RU. In the RU allocation Sub-field, thevalue of the above RU allocation pattern is set. In other fields also,values (common to the AP 1) are set to generate the SIG 1 field. Thecontroller 101 transmits the physical packet containing the legacyfield, the SIG 1 field, and the MAC frames addressed to the terminalsselected above. More specifically, the controller 101 transmits theheader containing the legacy field and the SIG 1 field using at thechannel width band, and transmits the MAC frames, subsequent to theheader, addressed to the selected terminals via the RUs allocatedrespectively to the terminals. Of a plurality of RUs included in thechannel width band, the RU allocated to no terminal by the controller101 is not used for the transmission.

The controller 101 may access a storage device for storing theinformation to be transmitted to the terminal or the informationreceived from the terminal, or the both of these to read out theinformation. The storage device may be an internal memory device, anexternal memory device, a volatile memory device, or a non-volatilememory device. The storage device may also be an SSD, a hard disk or thelike other than the memory.

The above described isolation of the processes of the controller 101 andthe transmitter 102 is an example, and another form may be used. Forexample, the controller 101 may perform the process until the digitalregion process and the DA conversion, and the transmitter 102 mayperform process subsequent to the DA conversion. As for the isolation ofthe processes of the controller 101 and the receiver 103, similarly, thereceiver 103 may perform the process before the AD conversion and thecontroller 101 may perform the digital region process includingprocesses following the AD conversion. As an example, the basebandintegrated circuitry in accordance with the present embodimentcorresponds to the section that carries out the processing of thephysical layer and the section that carries out the processing of the DAconversion in the controller 101 and the transmitter 102, and thesection that carries out the processing processes including andfollowing the AD conversion in the receiver 103. The RF integratedcircuitry corresponds to the section that carries out the processingprocesses following the DA conversion in the transmitter 102, and thesection that carries out the processing processes prior to the ADconversion in the receiver 103. The integrated circuitry for thewireless communication in accordance with the present embodimentincludes at least a baseband integrated circuitry from the basebandintegrated circuitry and the RF integrated circuitry. The processingprocesses between blocks or processing processes between the basebandintegrated circuitry and the RF integrated circuitry may be isolatedfrom each other in accordance with any method other than those describedherein.

FIG. 13A shows the configuration in the case where the communicationbetween the APs is performed using the same communication scheme as theterminal, but the communication between the APs may be performed usinganother scheme such as the wired communication. An exemplaryconfiguration in that case is shown in FIG. 13B. There are provided atransmitter 105 and a receiver 106 for the communication between theAPs. A wired IF 107, which is connected to the wired network, outputs asignal of a frame or packet received from the transmitter 105 to thewired network and transfers a signal of a frame or packet received fromthe wired network to the receiver 106. The transmitter and the receiver106 basically operate similar to the transmitter 105 and the receiver106 except for an operation depending on a protocol. For example, thetransmitter 105 subjects the frame or packet transferred from controller101 to modulation, DA conversion, filtering process, frequencyconversion, amplification and the like, and outputs the signal afterbeing amplified to the wired IF 107. The receiver 106 subjects thesignal received from the wired IF 107 to amplification, frequencyconversion, filtering process, AD conversion, demodulation and the liketo acquire the frame or the packet, and transfers the acquired frame orpacket to the controller 101.

FIG. 14 is a functional block diagram of the wireless communicationdevice equipped in the terminal. The wireless communication deviceequipped in the terminals 11 to 16, 21 to 23, 27 to 29 in FIG. 1 hasthis configuration.

The wireless communication device includes a controller 201, atransmitter 202, a receiver 203, at least one antenna 1, and a buffer204. The controller 201 corresponds to controlling circuitry or abaseband integrated circuitry which controls communication with the AP,and the transmitter 202 and the receiver 203 form a wirelesscommunicator or an RF integrated circuitry which transmits and receivesframes as an example. A process of the controller 201, and all or a partof a digital region process of the transmitter 202 and the receiver 203may be performed by software (program) executing on a processor such asa CPU, or may be performed by hardware, or may be performed by the bothof software and hardware. The terminal may include a processorperforming the process of the controller 201, all or a part of thetransmitter 202 and the receiver 203.

The buffer 204 is a storage for transferring a frame and the likebetween an upper layer and the controller 201. The buffer 204 may be avolatile memory such as a DRAM or a non-volatile memory such as a NAND,or an MRAM. The upper layer generates the frames to be transmitted toother terminals and APs or other devices on the network such as a serverand stores the generated frames in the buffer 204, or receives, from thecontroller 201 via the buffer 204, the frames received from otherterminals, APs and devices. The upper layer may perform an uppercommunication process than a MAC layer such as a TCP/IP or a UDP/IP. TheTCP/IP or the UDP/IP may be performed in the controller 201 and theupper layer may perform a process of an application layer of processingthe data upper than the TCP/IP or the UDP/IP. An operation of the upperlayer may be performed by software (program) processing by a processorsuch as a CPU, or may be performed by hardware, or may be performed bythe both of the software and the hardware.

The controller 201 mainly performs a process of the MAC layer. Thecontroller 201 transmits and receives the frames via the transmitter 202and the receiver 203 to and from the AP to control the communicationwith the AP. The controller 201 may include a clock generator generatinga clock to manage an internal time using the clock generated by theclock generator. The controller 201 may output externally the clockcreated by the clock generator. Alternatively, the controller 201 mayreceive a clock generated by an external clock generator to manage aninternal time using the relevant clock generated.

The controller 201, as an example, receives the beacon frame to graspthe attribute and synchronization information of BSS of the AP and thentransmits an association request to the AP to perform an associationprocess in response to the received beacon. Thereby, the controller 201exchanges required information on capability or an attribute etc. eachother (which may include capability information of whether to be capableof OFDMA) and establishes the wireless link with the AP. The controller201 may perform a process such as an authentication process if necessarybefore the association process. The controller 201 periodically checksthe buffer 204 to confirm the state of the buffer 204. Alternatively,the controller 201 may check the state of the buffer 204 according to atrigger given from an external device. Once the controller 201 confirmsthe existence of the frame such as the data frame to be transmitted tothe AP, it may transmit, after acquiring the access right to thewireless medium (transmission right) in accordance with the CSMA/CA orthe like, the relevant frame via the transmitter 202 and the antenna 1A.

The transmitter 202 adds a physical header to a frame input from thecontroller 201 to generate a physical packet, and further performsphysical processing such as coding and modulation process. Thetransmitter 202 subjects the physical packet after being modulated to DAconversion, a filtering process to extract components of a desired band,frequency conversion (up-conversion) and the like to amplify signalsobtained through these processes by a pre-amplifier and radiate theamplified signals as radio waves from one or more antennas into thespace. In the case where a plurality of antennas are provided, atransmission system may be provided for each antenna such that theprocess of the physical layer is performed for each transmission systemto simultaneously transmit the same signals. A plurality of antennas maybe used to control the directivity for transmission. The transmitter 202may acquire from the controller 201 information required for generatinga part or all of the physical header. A part or all of the physicalheader may be added by the controller 201.

The signal received by the antenna 1A is processed in the receiver 203.The received signal is amplified in the receiver 203 by the LNA,subjected to frequency conversion (down-conversion) and a filteringprocess to extract components of the desired band. The extracted signalis further converted into digital signals through AD conversion andsubjected to the processes of the physical layer such as demodulation,error-correcting decode, and a process of the physical header, andthereafter, the frame such as a data frame is input to the controller201. A part or all of the processes of the physical header may beperformed by the controller 201.

Once the receiver 203 receives a signal transmitted by way of DL-OFDMAfrom the AP, it detects a value indicating the RU allocation patternfrom the RU allocation Sub-field in the SIG 1 field in the physicalheader. The receiver checks whether the terminal identifier of theterminal of itself is set in any of a plurality of User fields, if so,it identifies the RU regarding that User field on the basis of the RUallocation pattern. The receiver 203 decodes the signal of theidentified RU to acquire the frame and transfers the acquired frame tothe controller 201. If the transferred frame is a frame requiring anacknowledgement response, the controller 201 generates anacknowledgement response frame on the basis of a check result of theframe and transmits the acknowledgement response frame. Theacknowledgement response frame may be transmitted by way of thesingle-user transmission or by way of the multiuser transmission(UL-OFDMA, UL-MU-MIMO or the like) with other terminals. The single-usertransmission may be performed after elapse of a predetermined certaintime period from receiving the frame, or by performing the carrier senseand a back-off operation in accordance with the CSMA/CA to acquire theaccess right with respect to the wireless medium. A part of DL-OFDMAsignal reception process described here may be performed by thecontroller 201.

The controller 201 may access a storage device that stores eitherinformation to be notified to the AP or the information notified fromthe AP or both of these pieces of information and read the information.The storage device may be an internal memory device, an external memorydevice, a volatile memory device, or a non-volatile memory device. Thestorage device may also be an SSD, a hard disk or the like other thanthe memory.

The above described isolation of the processes of the controller 201 andthe transmitter 202 is an example, and another form may be used. Forexample, the controller 201 may perform the process until the digitalregion process and the DA conversion, and the transmitter 202 mayperform process subsequent to the DA conversion. As for the isolation ofthe processes of the controller 201 and the receiver 203, similarly, thereceiver 203 may perform the process before the AD conversion and thecontroller 201 may perform the digital region process includingprocesses following the AD conversion. As an example, the basebandintegrated circuitry in accordance with the present embodimentcorresponds to the section that carries out the processing of thephysical layer and the section that carries out the processing of the DAconversion in the controller 201 and the transmitter 202, and thesection that carries out the processing processes including andfollowing the AD conversion in the receiver 203. The RF integratedcircuitry corresponds to the section that carries out the processingprocesses following the DA conversion in the transmitter 202, and thesection that carries out the processing processes prior to the ADconversion in the receiver 203. The integrated circuitry for thewireless communication in accordance with the present embodimentincludes at least a baseband integrated circuitry from the basebandintegrated circuitry and the RF integrated circuitry. The processingprocesses between blocks or processing processes between the basebandintegrated circuitry and the RF integrated circuitry may be isolatedfrom each other in accordance with any method other than those describedherein.

FIG. 15A is a flowchart of a first exemplary operation of the APaccording to the first embodiment (corresponding to the operation of theAP 1 in FIG. 12).

The AP determines to perform DL-OFDMA at an arbitrary timing, and then,determines the RU allocation pattern to be used (see FIG. 3) anddetermines the RU for FFR from among a plurality of RUs corresponding tothe RU allocation pattern (S101).

The AP selects one or more terminals as targets to which DL-OFDMA is tobe performed from among terminals establishing the wireless link (S102).Also, the AP allocates one or more RUs (at least the RU for FFR of theRU for FFR and the usual RU) to the terminals (S102 also).

The AP determines the MCS, the packet length (PPDU length or the like),and other parameters with respect to the selected terminals as needed.

The AP transmits as the FFR information, to the cooperative partner AP,the FFR-on information (identifier of the RU for FFR), the FFRcorrespondence information (information associating the identifier ofthe RU with the terminal allocation information (STAID or the like) ofthe terminal allocated with the relevant RU), and the value of the RUallocation pattern (S103).

Once the AP receives the FFR information from the partner AP or after acertain time period elapses (S104), the AP transmits the DL-MU startnotification frame specifying the execution timing for DL-OFDMA (S105).The DL-MU start notification frame is assumed to be a control frame, butmay be a management frame or a data frame. When the execution timing(predetermined timing) specified in the DL-MU start notification arrives(S106), the AP performs DL-OFDMA (S107).

Concretely, the AP sets the terminal allocation information (terminalidentifier or the like) of each terminal selected above in a field (Usefield) regarding the RU allocated to the relevant terminal. On the basisof the FFR information received from the partner AP, the AP sets theterminal allocation information of the terminal allocated with the RU(usual RU) which is used by the partner AP in a field (User field)regarding the relevant usual RU. In the RU allocation Sub-field, thevalue of the RU allocation pattern is set. In other fields in the SIG 1field also, values (common to the AP 2) are set. The AP transmits thephysical packet containing the legacy field, the SIG 1 field, and theMAC frames addressed to the terminals selected above. More specifically,the AP transmits the header containing the legacy fields and the SIG 1field using at the channel width band, and transmits the MAC frames,subsequent to the header, addressed to the terminals via the RUsallocated respectively to the terminals. Of a plurality of RUs includedin the channel width band, the RU allocated to no terminal by the AP isnot used for the transmission.

FIG. 15B is a flowchart of a second exemplary operation of the APaccording to the first embodiment (corresponding to the operation of theAP 2 in FIG. 12).

Once the AP receives the FFR information from the partner AP, itdetermines to perform DL-OFDMA (S201).

The AP grasps the RU allocation pattern and the RU for FFR on the basisof the FFR information (S202).

The AP selects, as the terminal allocated with the RU for FFR, fromamong the terminals (terminals compliant with OFDMA) establishing thewireless link, a terminal having a terminal identifier the same as theterminal identifier of the terminal to which the partner AP allocatesthe same RU for FFR (S203). The AP selects the terminal allocated withthe RU not used by the partner AP of the usual RUs as needed (S203also).

The AP determines the MCS, the packet length (PPDU length or the like),and other parameters with respect to the selected terminals as needed.In this case, with respect to the terminal allocated with the RU forFFR, determined are values the same as those for the terminal to whichthe partner AP allocates the same RU for FFR. The AP transmits as theFFR information, to the cooperative partner AP, information associatingthe identifier of the usual RU to be used with the terminal allocationinformation of the terminal allocated with the relevant usual RU (S204).

The AP grasps the execution timing for DL-OFDMA by receiving the DL-MUstart notification frame from the partner AP (S205). When the executiontiming (predetermined timing) specified in the DL-MU start notificationarrives (S206), the AP performs DL-OFDMA (S207).

Concretely, the AP sets the terminal allocation information (terminalidentifier or the like) of each terminal selected above in a field (Usefield) regarding the RU allocated to the terminal. On the basis of theFFR information received from the partner AP, the AP sets the terminalallocation information of the terminal allocated with the RU (usual RU)which is used by the partner AP in a field (User field) regarding therelevant usual RU. In the RU allocation Sub-field, the value of theabove RU allocation pattern is set. In other fields also, values (commonto the AP 1) are set to generate the SIG 1 field the same as the partnerAP. The AP transmits the physical packet containing the legacy field,the SIG 1 field, and the MAC frames addressed to the terminals selectedabove. More specifically, the AP transmits the header containing thelegacy field and the SIG 1 field using at the channel width band, andtransmits the MAC frames, subsequent to the header, addressed to theterminals via the RUs allocated respectively to the terminals. Of aplurality of RUs included in the channel width band, the RU allocated tono terminal by the AP is not used for the transmission.

As described above, according to the present embodiment, the AP 1 andthe AP 2 cooperate with each other to perform the FFR such that the AP 1and the AP 2 can use the same channel to perform DL-OFDMA with the highfrequency usage efficiency. In other words, both the AP 1 and the AP 2allocate the RU for FFR used by both the AP 1 and the AP 2 to theterminals having the same STAID such that the contents of the physicalheader parts (SIG 1 fields and the like) can be identical between the AP1 and the AP 2. By doing so, the terminal receiving the signals fromboth the AP 1 and the AP 2 can also decode the header part, and thus,can correctly receive the frame transmitted by way of DL-OFDMA from theAP to which the terminal itself belongs.

In this way, FFR for using the same RU by a plurality of APs at the sametime can be achieved in a wireless LAN system.

The present embodiment shows the example in which the FFR is performedbetween two APs, but the FFR can be performed also between three APs. Inthis case, the FFR information is exchanged between three APs tocooperate with each other, achieving the FFR similarly to the presentembodiment. The same holds for a second embodiment and third embodimentdescribed later.

Second Embodiment

In the first embodiment, FFR (Fractional Frequency Ruse) is performed byway of DL-OFDMA, but in the second embodiment, the FFR is performed byway of UL-OFDMA. In the case of UL-OFDMA, the AP transmits a framespecifying a plurality of terminal to perform UL-OFDMA and RUs used bythese terminals (hereinafter, referred to as a trigger frame: TF). Aplurality of terminals receiving the TF transmit at a predetermined sametiming respectively the MAC frames such the data frame (morespecifically, the physical packets containing the MAC frames) via thespecified RUs. This allows UL-OFDMA to be performed.

Similar to the first embodiment, assume the case where the AP 1allocates the RU #1 to the RU #6 to the terminals 11 to 16, and the AP 2allocates the RU #1 to the RU #3 and the RU #7 to the RU #9 to theterminals 21 to 23 and 27 to 29 (see FIG. 5).

FIG. 16 shows an exemplary format of the TF. The TF is defined based ona format of a general MAC frame. The TF includes a Frame Control field,a Duration/ID field, an Address 1 field, an Address 2 field, a COMMOMInfo field (common information field), and a plurality of Per User Infofields (terminal information fields).

As an example, the Type of the Frame Control field may be a valueindicating “control” and a value of the Subtype may be a value newlydefined for the TF. However, the frame type of the TF may be configuredto indicate not “control” but “management” or “date” non-exclusively.

In the Address 1 field, a broadcast address or a multicast address isset as the RA (Receiver Address), as an example. In the Address 2 field,the MAC address of the AP or the BSSID is set as the TA (TransmitterAddress).

In the COMMOM Info field, information notified commonly to a pluralityof terminals selected as the targets for UL-OFDMA is set. As an example,the information includes a duration of the frame to beuplink-transmitted or physical packet, classification of the frame to beuplink-transmitted, a length of an L-SIG field in a physical headeradded to the frame to be uplink-transmitted, and the like. Moreover,timing information of the uplink transmission may be set.

In each Per User Info field, information individually notified to theterminal is set. For example, the terminal identifier (STAID) of theterminal specified as the target for UL-OFDMA, the identifier of the RUallocated to the terminal, and the like are set. Additionally,information specifying the MCS applied to the frame to beuplink-transmitted may be set. If the each Per User Info field isassociated with the particular RU, the identifier of the RU may beconfigured to be omitted.

(First Exemplary Operation in Second Embodiment: Transmitting the SameTrigger Frame from Both APs Using Setting for Virtual AP)

FIG. 17 shows an exemplary operation sequence of a wireless LAN systemaccording to the present embodiment. Assume that each of the AP 1 andthe AP 2 is set to a setting of a Virtual AP capable of setting aplurality of BSSIDs. Concretely, as shown in FIG. 18, the AP 1 is set tohave a BSSID of the AP 1 itself (which is “A”) as well as a BSSID of theAP 2 (which is “B”) as a sub-BSSID. Similarly, the AP 2 is set to havethe BSSID of the AP 2 itself (which is “B”) as well as the BSSID of theAP 1 (which is “A”) as a sub-BSSID. Each of the terminals belonging tothe AP 1 and the AP 2 notifies to the AP whether or not it is capable ofreceiving, as the capability information, a frame whose Address 2 field(TA field) is set to a BSSID of an AP other than the AP (BSS) connectedto the terminal itself. The terminal notifying its capability ofreception can receive the frame whose TA field is set to the BSSID ofthe adjacent AP. Here, assume that the terminals 11 to 16 notify theircapabilities of reception to the AP 1, and the terminals 21 to 23 and 27to 29 notify their capabilities of reception to the AP 2. Thisnotification may be made by setting the capability information in anassociation request frame transmitted in the association or may be madeusing other frame such as a probe search frame.

The AP 1 and the AP 2 cooperate with each other to grasp the RU for FFRsuch that each of them acquires the terminal allocation information ofthe terminal allocated with the usual RU from the partner AP.

More specifically, the AP 1 determines the RU #1 to the RU #3 as the RUsfor FFR and allocates them respectively to the terminals 11 to 13.Further, the AP 1 allocates the RU #4 to the RU #6 as the usual RUsrespectively to the terminals 14 to 16. The AP 1 transmits as the FFRinformation, to the AP 2, information (FFR-on information) specifyingthe RU for FFR (the RU #1 to the RU #3), and FFR correspondenceinformation associating the RU #1 to the RU #6 with the terminalallocation information (STAID or the like) of the terminals (S21). TheAP 1 and the AP 2 may share in advance a rule concerning acorrespondence relationship between a Per User Info 1 to a Per User InfoN and the RUs in the trigger frame (TF). For example, a rule is sharedbetween the APs that the Per User Info 1 corresponds to the RU #1 andthe Per User Info 2 corresponds to the RU #2. As way to share, one ofthe AP 1 and the AP 2 may determine a rule and notify the rule to theother AP. Alternatively, a rule may be defined in the specification orthe standard.

The AP 2 grasps that the RU #1 to the RU #3 are the RUs for FFR on thebasis of the FFR-on information included in the FFR information receivedfrom the AP 1. The AP 2 allocates the RU #1 to the RU #3 respectively tothe terminals 21 to 23 having the STAIDs (the ID 1 to the ID 3) the sameas the AP 1 on the basis of the FFR correspondence information (S22).The AP 2 allocates the RU #7 to the RU #9 not used by the AP 1respectively to the terminal 27 to the terminal 29 having the ID 7 tothe ID 9 as the STAIDs. The AP 2 transmits as the FFR information, tothe AP 1, information associating the RU #7 to the RU #9 with theterminal allocation information (STAID or the like) of the terminalsallocated with these RUs (S23).

The AP 1 transmits a UL-MU (Uplink Mufti-User) start notification framespecifying execution timing for UL-OFDMA to the AP 2 (S24).

When the execution timing for UL-OFDMA arrives, the AP 1 and the AP 2simultaneously transmit the TFs respectively (S25, S26). Morespecifically, the AP 1 sets the Per User Info 1 to the Per User Info 6in the TF to the terminal allocation information (STAIDs) of theterminals 11 to 16 and the RU identifiers, and sets the Per User Info 7to the Per User Info 9 to the terminal allocation information of theterminals 27 to 29 and the RU identifiers acquired from the AP 2. Inother fields in the TF also, required information is set. This allowsthe TF (hereafter, referred as a TF 1) to be generated. Then, the AP 1transmits the generated TF 1. More accurately, the AP 1 transmits thephysical packet having the physical header including the legacy field(L-STF, L-LTF, and L-SIG) added to the TF 1. The physical header and theTF 1 are transmitted at the channel width band (e.g., 20 MHz). Anotherfield may be added between the legacy field and the TF 1 in the physicalheader.

The AP 2 sets the Per User Info 1 to the Per User Info 3, the Per UserInfo 7 to the Per User Info 9 in the TF respectively to the terminalallocation information (STAID or the like) of the terminals 21 to 23 and27 to 29 and the RU identifiers, and sets the Per User Info 4 to the PerUser Info 6 respectively to the terminal allocation information of theterminals 14 to 16 and the RU identifiers acquired from the AP 1. In theAddress 2 field, not the BSSID (MAC address) of the AP 2 but the BSSID(MAC address) of the AP 1 is set. In other fields also, requiredinformation is set. This allows the TF (hereafter, referred as a TF 2)to be generated. In this case, other fields are also set similar to theTF 1 (for this purpose, the information may be exchanged between the AP1 and the AP 2 as needed). This allows values of all fields of the TF 2be the same as those of the TF 1. The AP 2 transmits the generated TF 2.More accurately, the AP 2 transmits the physical packet having thephysical header including the legacy field (L-STF, L-LTF, and L-SIG)added to the TF 2. The physical header and the TF 2 are transmitted atthe channel width band (e.g., 20 MHz). Similar to the TF 1, anotherfield may be added between the legacy field and the TF 2 in the physicalheader. In this case, the added field is also made to have the samevalue as that added in the AP 1. For this purpose, the information maybe exchanged in advance between the AP 1 and the AP 2 as needed.

Each of the terminals 11 to 16 receives the TF 1 transmitted from the AP1 and confirms the TA set in the Address 2 field to determine that asender is the AP 1 (that is, the TF 1 is a frame the terminal itself isto receive). Each of the terminals 11 to 16 identifies the Per Userfield set to the STAID of the terminal itself and detects theinformation such as the RU used for the uplink transmission from theidentified field. Each of the terminals 11 to 16 transmits, after elapseof a predetermined time period from receiving the TF 1, the MAC framessuch the data frame (more specifically, the physical packet having thephysical header added to the MAC frames) via the specified RU (S27). Thephysical header contains the legacy field and the SIG 1 field. In theSIG 1 field, any control information notified to the AP 1 is set. Theformat of the SIG 1 field may be different from the format of the SIG 1field in the physical packet subjected to DL-OFDMA transmission in thefirst embodiment. FIG. 19A shows a physical packet transmitted from theterminals 11 to 16. This allows UL-OFDMA to be performed between the AP1 and the terminals 11 to 16.

On the other hand, each of the terminals 21 to 23 and 29 receives the TF2 transmitted from the AP 2 and confirms the TA set in the Address 2field. Each terminal determines that although the sender AP is foundfrom the TA to be different from the AP the terminal itself belongs to,the TF 2 is a frame the terminal is to receive based on the setting ofthe Virtual AP. Each of the terminals 21 to 23 and 29 identifies the PerUser field set to the STAID of the terminal itself and detects theinformation such as the RU used for the uplink transmission from theidentified field. Each of the terminals 21 to 23 and 29 transmits, afterelapse of a predetermined time period from receiving the TF 2, the MACframes such the data frame (more specifically, the physical packethaving the physical header added to the MAC frames) via the specified RU(S28). On the other hand, the terminals 27 and 28 simultaneously receivethe TF 1 transmitted from AP 1 and the TF 2 transmitted from the AP 2,but the physical headers of these TFs are identical and the contents ofthe TF 1 and the TF 2 are identical. This allows the terminals 27 and 28to correctly decode the received signals. Therefore, each of theterminals 27 and 28, similar to the terminals 21 to 23 and 29, detectsthe RU specified to the terminal itself and the like, and transmits theMAC frame (more specifically, the physical packet having the physicalheader added to the MAC frames) via the specified RU. The physicalheader contains the legacy field and the SIG 1 field. FIG. 19B shows aphysical packet transmitted from the terminals 21 to 23 and 27 to 29.This allows UL-OFDMA to be performed between the AP 2 and the terminals21 to 23 and 27 to 29.

The AP 1 may receive the uplink signals from the terminals not belongingto the AP 1 itself, for example, the terminals 27 and 28 in the overlaparea, but the reception operation in the AP 1 causes no problem becauseAP 1 does not use the RU #8 and the RU #9 used by these terminals 27 and28. The AP 2 may also receive the signal from the terminal 16, theterminal 15 or the like depending on the location of the terminal, butno problem is caused because the AP 2 does not use the RU #5, the RU #6or the like used by the terminal 16, the terminal 15 or the like.

(Second Exemplary Operation in Second Embodiment: Transmitting TriggerFrames Different from Each Other from Both APs Using Channel-BasedDL-OFDMA)

In the exemplary operation described above, the FFR information isexchanged between the AP 1 and the AP 2, and the BSSID of the AP 1 isused as the TA of the trigger frame generated by the AP 2 such that theTF 1 and the TF 2 generated respectively by the AP 1 and the AP 2 aremade to be the identical frames. This allows the terminal receiving theTF 1 and the TF 2 at the same time even to normally receive the TF 1 orthe TF 2. As another method, the AP 1 and the AP 2 may respectivelytransmit the trigger frames different from each other usingchannel-based DL-OFDMA. In the channel-based OFDMA, a plurality ofchannels (e.g., four channels of Ch1, Ch2, Ch3, and Ch4) aresimultaneously used to perform the transmission or the reception. Theterminal stands by at each of a plurality of channels. In this case, theVirtual AP with respect to each of the AP 1 and the AP 2 is notrequired.

Similar to the above, the FFR information is exchanged between the AP 1and the AP 2. Both APs determine the channels different from the otherwhich are used for the channel-based DL-OFDMA. For example, the AP 1determines to use the channels 1 and 2, and the AP 2 determines to usethe channels 3 and 4.

The AP 1 generates a TF (hereinafter, referred to as a TF 11) in whichthe Per User Info 1 to the Per User Info 6 are set to the terminalallocation information (STAID or the like) of the terminals 11 to 16,the RU identifiers, and the like. A TA of the TF 11 is the BSSID of theAP 1. The AP 2 generates a TF (hereinafter, referred to as a TF 12) inwhich the Per User Info 1 to the Per User Info 6 are set to the terminalallocation information of the terminals 21 to 23, and 27 to 29, the RUidentifiers, and the like. A TA of the TF 12 is the BSSID of the AP 2.However, in the case where the Per User Info field is not set to the RUidentifier but to a correspondence relationship between the relevantfield and RU, the terminal allocation information of each terminal isset in the Per User Info field corresponding to the RU allocated to theterminal.

As for the RU allocation by the AP 1 and the AP 2, similar to the aboveembodiments, the terminal in the neighbor area of the AP 1 and theterminal in the neighbor area of the AP 2 are allocated with the RU (RUfor FFR) the same between both APs as an example. The terminal in thedistant area of the AP 1 and the terminal in the distant area of the AP2 are allocated with the usual RUs different between the AP 1 and the AP2 (such that the RUs do not overlap between the APs). By doing so, thesignals transmitted from the respective neighbor areas of the AP 1 andthe AP 2 do not reach the partner AP (or, the received power is low evenif the signals reach), and therefore, each AP can correctly receive theframe from the terminal belonging to the AP itself in its neighbor area.As for the signals transmitted from the respective distant areas of theAP 1 and the AP 2, even if the signals reach the partner AP, because theRU (usual RU) used by each AP is different from that of its partner AP,no problem is caused in decoding the frame received from the terminalbelonging to the AP itself in its distant area.

The AP 1 transmits, for example, the TF 11 using the channel 1 and anarbitrary frame (which may be a frame the same as the TF 11 or a dataframe addressed to an terminal in the neighbor area A1) using thechannel 2. The TF 11 is a frame to instruct to perform UL-OFDMA usingthe channel 1. On the head side of each of these frames, added is thephysical header containing the legacy field, the SIG 1 field and thelike. In the SIG 1 fields at the channels 1 and 2, each of fields(subfields) for the channels 1 to 4 is set to an allocation target to beallocated with the channel, for example. The allocation target may bethe STAIDs of a plurality of terminals each of which is a receiver ofthe TF transmitted using the corresponding channel. In the case of thebroadcast, an ID defined for broadcast (referred to as a broadcast ID)may be adopted. In the case of the broadcast ID, all terminals are thereceivers of the TF. Here, assume that the terminal identifiers (or thebroadcast IDs) of the terminals 11 to 16 are set as the allocationtargets of the channels 1 and 2, and the terminal identifiers (or thebroadcast IDs) of the terminals 21 to 23 and 27 to 29 are set as theallocation targets of the channels 3 and 4 (note that the AP 1 graspsthe allocation targets of the channels 3 and 4 from the FFR informationacquired from the AP 2). The channels 3 and 4 may also be used totransmit the legacy field and the SIG 1 field the same as the channels 1and 2. FIG. 20A shows an exemplary physical packet the AP 1 transmits.Here, the channels 1 and 2 are used to transmit the same TF 11. Thechannels 3 and 4 are used to transmit the legacy field and the SIG 1field the same in their contents as the channels 1 and 2. Here, in theSIG 1 field, each of fields (subfields) for the channels 1 to 4 is setto the allocation target of the channel, which is an example however,may be configured to not include such information. Information requiredfor decoding the payload should be included. The AP 1 transmits the sameSIG 1 field using the channels 1 to 4, but such a limitation is notrequired so long as the terminal can receive independently for eachchannel.

Similarly, the AP 2 transmits the TF 12 using the channel 3 and anarbitrary frame (which may be a frame the same as the TF 12 or a dataframe addressed to a terminal in the neighbor area B1) using the channel4. The TF 12 is a frame to instruct to perform UL-OFDMA using thechannel 1. On the head side of each of these frames, added is thephysical header containing the legacy field, the SIG 1 field and thelike. The legacy field and the SIG 1 field are the same as thosetransmitted by the AP 1. In order to achieve this, a rule for settingthe terminal identifier in each of fields for the channels 1 to 4 in theSIG 1 field is shared in advance between the AP 1 and the AP 2. FIG. 20Bshows an exemplary physical packet the AP 2 transmits. Here, thechannels 3 and 4 are used to transmit the same TF 12. The channels 1 and2 are used to transmit the legacy field and the SIG 1 field the same intheir contents as the channels 3 and 4. The AP 2 transmits the same SIG1 field using the channels 1 to 4, but such a limitation may not berequired so long as the terminal can receive independently for eachchannel.

The terminals 11 to 16 belonging to the AP 1 stand by, for example, atthe channels 1 to 4, and then, decodes and analyzes the TF 11 receivedusing the channel 1 or 2 so as to detect the RUs allocated to theterminals themselves to perform UL-OFDMA transmission (see FIG. 19A). Ifa data frame addressed to any terminal is transmitted using the channel2, that terminal detects from the SIG 1 field that the data frameaddressed to the terminal itself is transmitted using the channel 2 andreceives the data frame. The terminals 21 to 23 and 27 to 29 belongingto the AP 2 stand by, for example, at the channels 1 to 4, and then,decodes and analyzes the TF 12 received using the channel 3 or 4 so asto detect the RUs allocated to the terminals themselves to performUL-OFDMA transmission (see FIG. 19B). If a data frame addressed to anyterminal is transmitted using the channel 4, that terminal detects fromthe SIG 1 field that the data frame addressed to the terminal itself istransmitted using the channel 4 and also receives the data frame.

As described above, according to the present embodiment, the AP 1 andthe AP 2 can use the same channel to perform UL-OFDMA with the highfrequency usage efficiency. In other words, the AP 1 and the AP 2transmit the trigger frame having the same content (more specifically,the physical packet having the same content), or the trigger frame usingthe different channel to allow the terminal in the overlap area also tocorrectly receive the trigger frame transmitted from the AP to which theterminal itself belong. Therefore, also in the case of UL-OFDMA, the FFRfor using the same RU by a plurality of APs at the same time can beachieved with the high frequency usage efficiency.

Third Embodiment

In the first embodiment, the AP 1 and the AP 2 allocate the identical RU(RU for FFR), of a plurality of RUs used for DL-OFDMA, to the terminalshaving the same STAID to achieve the high efficient FFR. In the thirdembodiment, the AP 1 and the AP 2 use the identical RU (RU for FFR), ofa plurality of RUs used for DL-OFDMA, to perform the downlink multiuserMIMO (Multi-Input and Multi-Output) (DL-MU-MIMO) to achieve the highefficient FFR. In other words, of a plurality of RUs used for DL-OFDMA,a part of the RUs (RU for FFR) is used to perform the DL-MU-MIMO. Thisscheme is designated as DL-OFDMA & MU-MIMO.

In order to perform the DL-MU-MIMO via the RU, an RU greater than orequal to 106 tones needs to be used, as an example. For this reason, asthe RU allocation pattern, the allocation patterns No. 16 to No. 23 inFIG. 3 can be used, for example. Hereinafter, the allocation pattern No.23 is assumed. FIG. 21 shows the allocation pattern No. 23. As shown inthe figure, a 106-tone RU is designated as the RU #1 (or RU for FFR),and five 26-tone RUs are designated as the RU #2, the RU #3, the RU #4,the RU #5, and the RU #6 in ascending order of the frequency.

Assume a case where the AP 1 performs the DL-MU-MIMO transmission to theterminal 11 and the terminal 12 via the RU #1 (the DL-MU-MIMOtransmission with the number of multiplexes is two), to the terminal 14via the RU #2, and to the terminal 15 via the RU #3. The transmissionsto the terminal 14 and the terminal 15 may be performed by way of thebeam forming or non-directional transmission (omnidirectionaltransmission). In addition, assume a case where the AP 2 performs theDL-MU-MIMO transmission to the terminal 21 via the RU #1 (the DL-MU-MIMOtransmission with the number of multiplexes is one), to the terminal 23via the RU #4, to the terminal 27 via the RU #5, and to the terminal 28via the RU #6. The transmissions to the terminal 23, the terminal 27,and the terminal 28 may be performed by way of the beam forming or thenon-directional transmission (omnidirectional transmission). Here,terminals as targets for the DL-MU-MIMO transmission are the terminalsin the neighbor areas A1 and B1, without limitation.

Here, in the case of the pattern No. 23, a value set in the RUallocation Sub-field in FIG. 7 may be “01000y₂y₁y₀”. A value of “y₂y₁y₀”may take a value in a range from “000” to “111”. The value of “y₂y₁y₀”is set to a value corresponding to the number of multiplexes of thetransmission via the 106-tone RU (RU #1). In the example, via the RU #1,the AP 1 performs double multiplexing transmission and the AP 2 performssingle multiplexing transmission, and accordingly, a value representingthe number of multiplexes of 3, that is “011”, is set to “y₂y₁y₀”. Inother words, the RU allocation Sub-field is set to “01000011”. Anexemplary setting is shown in FIG. 22A. Both the AP 1 and the AP 2 setthis value.

The User Specific field subsequent to the RU allocation Sub-fieldcontains the User field #1 to the User field #3 corresponding to thenumber of multiplexes of 3, and the User field #4 to the User field #8respectively corresponding to the 26-tone RU #2 to RU #6. In otherwords, as shown in FIG. 22B, three User fields are used with respect tothe 106-tone RU, and one User field is used with respect to each of the26-tone RU #2 to RU #6. By changing the value of “y₂y₁y₀”, the number ofthe User fields (the number of multiplexes) with respect to the 106-toneRU changes. Such a rule is recognized in common to the APs and theterminals.

As for the terminals 11 and 12 as the targets for the DL-MU-MIMOtransmission, the AP 1 sets the terminal allocation information of theterminal 11 in the predetermined User field #1 of the plural User fields#1 to #3, and the terminal allocation information of the terminal 12 inthe predetermined User field #2 of the plural User fields #1 to #3. Theterminal allocation information includes the STAID, informationidentifying a stream, the number of the streams, the MCS, and the like,for example. The AP 1 sets the terminal allocation information of theterminal 14 in the User field #4, and the terminal allocationinformation of the terminal 15 in the User field #5. The terminalallocation information of the terminals 14 and 15 may include the STAID,the number of the streams, whether to receive the beam forming, the MCS,and the like, for example.

As for the terminals 21 as the target for the DL-MU-MIMO transmission,the AP 2 sets the terminal allocation information of the terminal 21 inthe predetermined User field #3 of the plural User fields #1 to #3.Moreover, the AP 2 sets the terminal allocation information of theterminal 23, the terminal 27, and the terminal 28 respectively in theUser field #6 to the User field #8.

Further, the AP 2 cooperates with the AP 1 to acquire the information ofthe RUs (RU #1, RU #2, RU #4, and RU #5) allocated by the AP 1 to theterminal 11, the terminal 12, the terminal 14, and the terminal 15, andthe terminal allocation information of these terminals. Then, the AP 2sets the terminal allocation information of the terminals 11 and 12acquired from the AP 1 respectively in the User fields #1 and #2, of theUser fields #1 to #3 corresponding to the RU #1, and also sets theterminal allocation information of the terminals 14 and 15 acquired fromthe AP 1 respectively in the User fields #4 and #5 corresponding to theRU #4 and the RU #5.

The AP 1 also acquires the information of the RUs (RU #1, RU #4, RU #5,and RU #6) allocated by the AP 2 to the terminal 21, the terminal 23,the terminal 27, and the terminal 28, and the terminal allocationinformation of these terminals. Then, the AP 1 sets the terminalallocation information of the terminals 21 acquired from the AP 2 in theUser field #3, of the User fields #1 to #3 corresponding to the RU #1,and also sets the terminal allocation information of the terminals 23,27 and 28 acquired from the AP 2 respectively in the User fields #6, #7,and #8 corresponding to the RU #4, #5, and the RU #6.

In accordance with the above operation, the User fields #1 to #8 set bythe AP 1 and the User fields #1 to #8 set by the AP 2 become identical.As described above, the RU allocation Sub-fields are set to the valuethe same between the AP 1 and the AP 2.

FIG. 23 shows an operation sequence of a wireless LAN system accordingto the present embodiment. Once the AP 1 determines to perform DL-OFDMA& MU-MIMO transmission in cooperation with the AP 2, it transmits dataincluding information (FFR information) required for the cooperation tothe AP 2 (S31).

More specifically, the AP 1 determines the RU allocation pattern havinga RU having the number of tones capable of the MU-MIMO, and determinesthe relevant RU having the number of tones as the RU for FFR. The AP 1also determines the maximum number of multiplexes for the DL-MU-MIMOperformed using the RU for FFR. The maximum number of multiplexes may bethat obtained by multiplying the number of multiplexes the AP 1 desiresby a certain value, or that obtained by adding the number of multiplexesthe AP 2 desires which is notified in advance from the AP 2 to thenumber of multiplexes the AP 1 desires. The AP 1 determines a value tobe set in the RU allocation Sub-field (hereinafter, referred to as apattern setting value) from the determined RU allocation pattern and themaximum number of multiplexes.

Here, similar to the above example, the AP 1 selects the RU allocationpattern No. 23 to determine the RU #1 in FIG. 21 as the RU for FFR. Themaximum number of multiplexes is determined to be “3”, and the patternsetting value is set to “01000011”. The terminals 11 and 12 are selectedas the terminals to perform the DL-MU-MIMO. The terminals 14 and 15 areselected as the terminals to be allocated with the RU #2 and the RU #3which are the RUs (usual RUs) other than the RU for FFR.

On the basis of the above determination, the AP 1 generates the FFRinformation and transmits the generated FFR information to the AP 2.Concretely, the AP 1 transmits the pattern setting value (the RUallocation pattern and the maximum number of multiplexes) and theinformation (FFR-on information) specifying the RU for FFR (RU #1).Further, the terminal allocation information of the terminals 11 and 12which use the RU #1 and the terminal allocation information of theterminals 14 and 15 to which the RU #2 and the RU #3 are allocated.Information may be further transmitted which indicates that the terminal11 corresponds to the User field #1 and the terminal 12 corresponds tothe User field #2. The details of the terminal allocation informationare as described above.

The AP 2 grasps the RU allocation pattern to be used this time on thebasis of the FFR information received from the AP 1, and grasps that theRU #1 is the RU for FFR and the maximum number of multiplexes is “3”.The AP 2 determines that the RU #2 and the RU #3 are used by the AP 1,and thus, the AP 2 itself can use the RU #4 to the RU #6. The AP 2determines that, on the basis that the AP 1 already allocates the RU #1to two terminals, the AP 2 itself can allocate the RU #1 to only oneterminal. Then, assume that the AP 2 determines to allocate the RU #1 tothe terminal 21. Alternatively, assume that the AP 2 determines toallocate the RU #4 to RU #6 to the terminal 23, the terminal 27, and theterminal 29. The AP 2 transmits as the FFR information, to the AP 1, theterminal allocation information of the terminal 21 allocated with the RU#1, and the terminal allocation information of the terminals 23, 27, and28 allocated with the RU #4 to the RU #6 (S32).

Once the AP 1 receives the FFR information from the AP 2, it determinesan execution timing for DL-OFDMA & MU-MIMO and transmits the DL-MU startnotification frame specifying the execution timing to the AP 2 (S33).

When the execution timing for DL-OFDMA & MU-MIMO arrives, the AP 1 andthe AP 2 perform DL-OFDMA & MU-MIMO transmission (S34, S35). This allowsthe AP 1 and the AP 2 to simultaneously perform DL-OFDMA & MU-MIMOtransmission.

FIG. 24A and FIG. 24B respectively show exemplary physical packets theAP 1 and the AP 2 transmit. The legacy field and the SIG 1 field(containing the RU allocation Sub-field and the User Specific field) inthe physical packet transmitted by the AP 1 are the same as those in thephysical packet transmitted by the AP 2. The legacy field and the SIG 1field are transmitted at the channel width band. Via the RU #1, the SIG2 field and the MAC frame are transmitted by spatial multiplexing(double multiplexing) from the AP 1 to the terminal 11 and the terminal12, and the SIG 2 field and the MAC frame are transmitted by spatialmultiplexing (single multiplexing) from the AP 2 to the terminal 21.

Here, the terminals 11 and 12 hold in advance space separationinformation (bit patterns) orthogonal to each other. The SIG 2 fieldtransmitted by the AP 1 via the R1 #1 is multiplexed by signals(preamble signals) having these bit patterns orthogonal to each other.This allows each of the terminals 11 and 12 to extract signals bysubjecting the signal of the SIG 2 field to an arithmetic on the basisof the space separation information of the terminal itself. Theextracted signal is a signal whose amplifier and phase are varied owingto the channel. Each of the terminals 11 and 12 calculates a channelresponse on the basis of this signal and the signal represented by thespace separation information to separate a stream addressed to theterminal itself subsequent to the SIG 2 field using the channelresponse. This allows the MAC frame to be acquired. The separatingmethod of the stream is not limited to this, and any other method may beadapted. Examples of the above space separation information may includerows and columns in an orthogonal matrix. The space separationinformation may be, besides being held by the terminal in advance, setin the User field for each terminal or the like in the SIG 1 field as amethod. The SIG 2 field transmitted by the AP 2 via the RU #2 alsoincludes the bit pattern the same as that of the space separationinformation held by the terminal 21, similarly.

The terminals 14 and 15 specified in the physical packet transmitted bythe AP 1, similarly to the first embodiment, respectively interpret theSIG 1 field, identify the RU #2 and the RU #3 allocated to the terminalsthemselves, and decode the signals of the identified RUs to receive theMAC frames (S36). The SIG 2 field transmitted via the RU #2 and the RU#3 may be a training field or other field, for example. Each of theterminals 11 and 12 separates a stream addressed to the terminal itselffrom the signal transmitted via the RU #1 using the above method toreceive the MAC frame.

On the other hand, the terminals 23, 27 and 28 specified in the physicalpacket transmitted by the AP 2, similarly to the first embodiment,respectively interpret the SIG 1 field, identify the RU #4, the RU #5and the RU #6 allocated to the terminals themselves, and decode thesignals of the identified RUs to receive the MAC frames (S37). The SIG 2field transmitted via the RU #4, the RU #5 and the RU #6 may be atraining field or other field, for example. Terminal 21 separates astream addressed to the terminal itself from the signal transmitted viathe RU #1 using the above method to receive the MAC frame (S37 also).The terminal 27 and the terminal 28 simultaneously receive the signalsof the physical packets from both the AP 1 and the AP 2, but since thelegacy fields and the SIG 1 fields of them are the same, the receivedsignals can be correctly decoded to identify the RUs allocated to theterminals themselves.

The RU allocation pattern No. 23 used in the above example includes onlyone RU greater than or equal to 106 tones, but the RU allocation patternincluding two or more relevant RUs may be used. In this case, each oftwo or more RUs can perform the DL-MU-MIMO. For example, in a case wherethe RU allocation pattern No. 24 in FIG. 3 is used, there are two106-tone RUs (RUs for FFR). For this reason, each of two RUs for FFR canperform the DL-MU-MIMO. In this case, the pattern setting valuesimultaneously representing the RU allocation pattern, the number ofmultiplexes in the transmission via the RU for FFR on the left side (lowfrequency side), and the number of multiplexes in the transmission viathe RU for FFR on the right side (high frequency side) may be set in theRU Allocation Sub-field.

For example, in the case of the RU allocation pattern No. 24, thepattern setting value may be represented by a form of “01y₂y₁y₀z₂z₁z₀”.A value of “y₂y₁y₀” is a value in a range from “000” to “111”, and avalue of “z₂z₁z₀” is a value in a range from “000” to “111”. The valueof “y₂y₁y₀” is set to a value corresponding to the maximum number ofmultiplexes in the transmission performed via the RU for FFR on the leftside, and the value of “z₂z₁z₀” is set to a value corresponding to themaximum number of multiplexes in the transmission performed via the RUfor FFR on the right side. For example, if the maximum number ofmultiplexes for the RU on the left side is set to “3”, the value of“y₂y₁y₀” is set to “011”, and if the maximum number of multiplexes forthe RU on the right side is set to “4”, the value of “z₂z₁z₀” is set to“100”.

As described above, according to the present embodiment, the AP 1 andthe AP 2 use the identical RU (RU for FFR), of a plurality of RUs usedfor DL-OFDMA, to perform the DL-MU-MIMO, and the contents of thephysical header parts (SIG 1 fields or the like) are identical betweenthe AP 1 and the AP 2. By doing so, the terminal receiving the signalsfrom both the AP 1 and the AP 2 can also decode the header part, andthus, can correctly receive the frame transmitted from the AP to whichthe terminal itself belongs. Therefore, a FFR having high frequencyefficiency can be achieved in a wireless LAN system.

Fourth Embodiment

FIG. 25 is a functional block diagram of a base station (access point)400 according to the embodiment. The access point includes acommunication processor 401, a transmitter 402, a receiver 403, antennas42A, 42B, 42C, and 42D, a network processor 404, a wired I/F 405, and amemory 406. The access point 400 is connected to a server 407 throughthe wired I/F 405. At least a former of the communication processor 401and the network processor 404 has functions similar to the controller inthe first embodiment. The transmitter 402 and the receiver 403 havefunctions similar to the transmitter and the receiver described in thefirst embodiment. Alternatively, the transmitter 402 and the receiver403 may perform analog domain processing in the transmitter and thereceiver and the network processor 404 may perform digital domainprocessing in the transmitter and the receiver in the first embodiment.The communication processor 404 has functions similar to the upper layerprocessor. The communication processor 401 may internally possess abuffer for transferring data to and from the network processor 404. Thebuffer may be a volatile memory, such as an SRAM or a DRAM, or may be anon-volatile memory, such as a NAND or an MRAM.

The network processor 404 controls data exchange with the communicationprocessor 401, data writing and reading to and from the memory 406, andcommunication with the server 407 through the wired I/F 405. The networkprocessor 404 may execute a higher communication process of the MAClayer, such as TCP/IP or UDP/IP, or a process of the application layer.The operation of the network processor may be performed throughprocessing of software (program) by a processor, such as a CPU. Theoperation may be performed by hardware or may be performed by both ofthe software and the hardware.

For example, the communication processor 401 corresponds to a basebandintegrated circuit, and the transmitter 402 and the receiver 403correspond to an RF integrated circuit that transmits and receivesframes. The communication processor 401 and the network processor 404may be formed by one integrated circuit (one chip). Parts that executeprocessing of digital areas of the transmitter 402 and the receiver 403and parts that execute processing of analog areas may be formed bydifferent chips. The communication processor 401 may execute a highercommunication process of the MAC layer, such as TCP/IP or UDP/IP.Although the number of antennas is four here, it is only necessary thatat least one antenna is included.

The memory 406 saves data received from the server 407 and data receivedby the receiver 402. The memory 406 may be, for example, a volatilememory, such as a DRAM, or may be a non-volatile memory, such as a NANDor an MRAM. The memory 406 may be an SSD, an HDD, an SD card, an eMMC,or the like. The memory 406 may be provided outside of the base station400.

The wired I/F 405 transmits and receives data to and from the server407. Although the communication with the server 407 is performed througha wire in the present embodiment, the communication with the server 407may be performed wirelessly.

The server 407 is a communication device that returns a responseincluding requested data in response to reception of a data forwardrequest for requesting transmission of the data. Examples of the server407 include an HTTP server (Web server) and an FTP server. However, theserver 407 is not limited to these as long as the server 407 has afunction of returning the requested data. The server 407 may be acommunication device operated by the user, such as a PC or a smartphone.The server 407 may wirelessly communicate with the base station 400.

When the STA belonging to the BSS of the base station 400 issues aforward request of data for the server 407, a packet regarding the dataforward request is transmitted to the base station 400. The base station400 receives the packet through the antennas 42A to 42D. The basestation 400 causes the receiver 403 to execute the process of thephysical layer and the like and causes the communication processor 401to execute the process of the MAC layer and the like.

The network processor 404 analyzes the packet received from thecommunication processor 401. Specifically, the network processor 404checks the destination IP address, the destination port number, and thelike. When the data of the packet is a data forward request such as anHTTP GET request, the network processor 404 checks whether the datarequested by the data forward request (for example, data in the URLrequested by the HTTP GET request) is cached (stored) in the memory 406.A table associating the URL (or reduced expression of the URL, such as ahash value or an identifier substituting the URL) and the data is storedin the memory 406. The fact that the data is cached in the memory 406will be expressed that the cache data exists in the memory 406.

When the cache data does not exist in the memory 406, the networkprocessor 404 transmits the data forward request to the server 407through the wired I/F 405. In other words, the network processor 404substitutes the STA to transmit the data forward request to the server407. Specifically, the network processor 404 generates an HTTP requestand executes protocol processing, such as adding the TCP/IP header, totransfer the packet to the wired I/F 405. The wired I/F 405 transmitsthe received packet to the server 407.

The wired I/F 405 receives, from the server 407, a packet that is aresponse to the data forward request. From the IP header of the packetreceived through the wired I/F 405, the network processor 404 figuresout that the packet is addressed to the STA and transfers the packet tothe communication processor 401. The communication processor 401executes processing of the MAC layer and the like for the packet. Thetransmitter 402 executes processing of the physical layer and the likeand transmits the packet addressed to the STA from the antennas 42A to42D. The network processor 404 associates the data received from theserver 407 with the URL (or reduced expression of the URL) and saves thecache data in the memory 406.

When the cache data exists in the memory 406, the network processor 404reads the data requested by the data forward request from the memory 406and transmits the data to the communication processor 401. Specifically,the network processor 404 adds the HTTP header or the like to the dataread from the memory 406 and executes protocol processing, such asadding the TCP/IP header, to transmit the packet to the communicationprocessor 401. In this case, the transmitter IP address of the packet isset to the same IP address as the server, and the transmitter portnumber is also set to the same port number as the server (destinationport number of the packet transmitted by the communication terminal),for example. Therefore, it can be viewed from the STA as ifcommunication with the server 407 is established. The communicationprocessor 401 executes processing of the MAC layer and the like for thepacket. The transmitter 402 executes processing of the physical layerand the like and transmits the packet addressed to the STA from theantennas 42A to 42D.

According to the operation, frequently accessed data is responded basedon the cache data saved in the memory 406, and the traffic between theserver 407 and the base station 400 can be reduced. Note that theoperation of the network processor 404 is not limited to the operationof the present embodiment. There is no problem in performing otheroperation when a general caching proxy is used, in which data isacquired from the server 407 in place of the STA, the data is cached inthe memory 406, and a response is made from the cache data of the memory406 for a data forward request of the same data.

The base station (access point) according to the present invention canbe applied for the base station in the above-stated any embodiment. Thetransmission of the frame, the data or the packet used in the anyembodiment may be carried out based on the cached data stored in thememory 406. Also, information obtained based on the frame, the data orthe packet received by the base station in the first to seventhembodiments may be cached in the memory 406. The frame transmitted bythe base station in the first to seventh embodiments may include thecached data or information based on the cached data. The informationbased on the cached data may include information on a size of the data,a size of a packet required for transmission of the data. Theinformation based on the cached data may include a modulation schemerequired for transmission of the data. The information based on thecached data may include information on existence or non-existence ofdata addressed to the terminal,

The base station (access point) according to the present invention canbe applied for the base station in the above-stated any embodiment. Inthe present embodiment, although the base station with the cachefunction is described, a terminal (STA) with the cache function can alsobe realized by the same block configuration as FIG. 25. In this case,the wired I/F 405 may be omitted. The transmission, by the terminal, ofthe frame, the data or the packet used in the any embodiment may becarried out based on the cached data stored in the memory 406. Also,information obtained based on the frame, the data or the packet receivedby the terminal in the any embodiment may be cached in the memory 406.The frame transmitted by the terminal in the first embodiment mayinclude the cached data or information based on the cached data. Theinformation based on the cached data may include information on a sizeof the data, a size of a packet required for transmission of the data.The information based on the cached data may include a modulation schemerequired for transmission of the data. The information based on thecached data may include information on existence or non-existence ofdata addressed to the terminal.

Fifth Embodiment

FIG. 26 shows an example of entire configuration of a terminal (non-APterminal) or a base station (AP). The example of configuration is justan example, and the present embodiment is not limited to this. Theterminal or the base station includes one or a plurality of antennas 1to n (n is an integer equal to or greater than 1), a wireless LAN module148, and a host system 149. The wireless LAN module 148 corresponds tothe wireless communication device according to any of the embodiments.The wireless LAN module 148 includes a host interface and is connectedto the host system 149 through the host interface. Other than theconnection to the host system 149 through the connection cable, thewireless LAN module 148 may be directly connected to the host system149. The wireless LAN module 148 can be mounted on a substrate bysoldering or the like and can be connected to the host system 149through wiring of the substrate. The host system 149 uses the wirelessLAN module 148 and the antennas 1 to n to communicate with externalapparatuses according to an arbitrary communication protocol. Thecommunication protocol may include the TCP/IP and a protocol of a layerhigher than that. Alternatively, the TCP/IP may be mounted on thewireless LAN module 148, and the host system 149 may execute only aprotocol in a layer higher than that. In this case, the configuration ofthe host system 149 can be simplified. Examples of the present terminalinclude a mobile terminal, a TV, a digital camera, a wearable device, atablet, a smartphone, a game device, a network storage device, amonitor, a digital audio player, a Web camera, a video camera, aprojector, a navigation system, an external adaptor, an internaladaptor, a set top box, a gateway, a printer server, a mobile accesspoint, a router, an enterprise/service provider access point, a portabledevice, a hand-held device, a vehicle and so on.

The wireless LAN module 148 (or the wireless communication device) mayhave functions of other wireless communication standards such as LTE(Long Term Evolution), LTE-Advanced (standards for mobile phones) aswell as the IEEE802.11.

FIG. 27 shows an example of hardware configuration of a WLAN module. Theconfiguration shown in the figure may be applied for each case in wherethe wireless communication device is mounted in non-AP terminal or in AP(Access Point) provided correspondingly to each function. That is, theconfiguration can be applied as specific examples of the wirelesscommunication device in any embodiment as described so far. In theconfiguration shown in figure, at least one antenna is included althougha plurality of antennas are included. In this case, a plurality of setsof a transmission system (116 and 122 to 125), a reception system (117,132 to 135), a PLL 142, a crystal oscillator (reference signal source)143, and a switch 145 may be arranged according to the antennas, andeach set may be connected to a control circuit 112. One or both of thePLL 142 and the crystal oscillator 143 correspond to an oscillatoraccording to the present embodiment.

The wireless LAN module (wireless communication device) includes abaseband IC (Integrated Circuit) 111, an RF (Radio Frequency) IC 121, abalun 125, the switch 145, and the antenna 147.

The baseband IC 111 includes the baseband circuit (control circuit) 112,a memory 113, a host interface 114, a CPU 115, a DAC (Digital to AnalogConverter) 116, and an ADC (Analog to Digital Converter) 117.

The baseband IC 111 and the RF IC 121 may be formed on the samesubstrate. The baseband IC 111 and the RF IC 121 may be formed by onechip. Both or one of the DAC 116 and the ADC 117 may be arranged on theRF IC 121 or may be arranged on another IC. Both or one of the memory113 and the CPU 115 may be arranged on an IC other than the baseband IC.

The memory 113 stores data to be transferred to and from the hostsystem. The memory 113 also stores one or both of information to betransmitted to the terminal or the base station and informationtransmitted from the terminal or the base station. The memory 113 mayalso store a program necessary for the execution of the CPU 115 and maybe used as a work area for the CPU 115 to execute the program. Thememory 113 may be a volatile memory, such as an SRAM or a DRAM, or maybe a non-volatile memory, such as a NAND or an MRAM.

The host interface 114 is an interface for connection to the hostsystem. The interface can be anything, such as UART, SPI, SDIO, USB, orPCI Express.

The CPU 115 is a processor that executes a program to control thebaseband circuit 112. The baseband circuit 112 mainly executes a processof the MAC layer and a process of the physical layer. One or both of thebaseband circuit 112 and the CPU 115 correspond to the communicationcontrol apparatus that controls communication, the controller thatcontrols communication, or controlling circuitry that controlscommunication.

At least one of the baseband circuit 112 or the CPU 115 may include aclock generator that generates a clock and may manage internal time bythe clock generated by the clock generator.

For the process of the physical layer, the baseband circuit 112 performsaddition of the physical header, coding, encryption, modulation process(which may include MIMO modulation), and the like of the frame to betransmitted and generates, for example, two types of digital basebandsignals (hereinafter, “digital I signal” and “digital Q signal”).

The DAC 116 performs DA conversion of signals input from the basebandcircuit 112. More specifically, the DAC 116 converts the digital Isignal to an analog I signal and converts the digital Q signal to ananalog Q signal. Note that a single system signal may be transmittedwithout performing quadrature modulation. When a plurality of antennasare included, and single system or multi-system transmission signalsequivalent to the number of antennas are to be distributed andtransmitted, the number of provided DACs and the like may correspond tothe number of antennas.

The RF IC 121 is, for example, one or both of an RF analog IC and a highfrequency IC. The RF IC 121 includes a filter 122, a mixer 123, apreamplifier (PA) 124, the PLL (Phase Locked Loop) 142, a low noiseamplifier (LNA) 134, a balun 135, a mixer 133, and a filter 132. Some ofthe elements may be arranged on the baseband IC 111 or another IC. Thefilters 122 and 132 may be bandpass filters or low pass filters.

The filter 122 extracts a signal of a desired band from each of theanalog I signal and the analog Q signal input from the DAC 116. The PLL142 uses an oscillation signal input from the crystal oscillator 143 andperforms one or both of division and multiplication of the oscillationsignal to thereby generate a signal at a certain frequency synchronizedwith the phase of the input signal. Note that the PLL 142 includes a VCO(Voltage Controlled Oscillator) and uses the VCO to perform feedbackcontrol based on the oscillation signal input from the crystaloscillator 143 to thereby obtain the signal at the certain frequency.The generated signal at the certain frequency is input to the mixer 123and the mixer 133. The PLL 142 is equivalent to an example of anoscillator that generates a signal at a certain frequency.

The mixer 123 uses the signal at the certain frequency supplied from thePLL 142 to up-convert the analog I signal and the analog Q signal passedthrough the filter 122 into a radio frequency. The preamplifier (PA)amplifies the analog I signal and the analog Q signal at the radiofrequency generated by the mixer 123, up to desired output power. Thebalun 125 is a converter for converting a balanced signal (differentialsignal) to an unbalanced signal (single-ended signal). Although thebalanced signal is handled by the RF IC 121, the unbalanced signal ishandled from the output of the RF IC 121 to the antenna 147. Therefore,the balun 125 performs the signal conversions.

The switch 145 is connected to the balun 125 on the transmission sideduring the transmission and is connected to the LNA 134 or the RF IC 121on the reception side during the reception. The baseband IC 111 or theRF IC 121 may control the switch 145. There may be another circuit thatcontrols the switch 145, and the circuit may control the switch 145.

The analog I signal and the analog Q signal at the radio frequencyamplified by the preamplifier 124 are subjected to balanced-unbalancedconversion by the balun 125 and are then emitted as radio waves to thespace from the antenna 147.

The antenna 147 may be a chip antenna, may be an antenna formed bywiring on a printed circuit board, or may be an antenna formed by usinga linear conductive element.

The LNA 134 in the RF IC 121 amplifies a signal received from theantenna 147 through the switch 145 up to a level that allowsdemodulation, while maintaining the noise low. The balun 135 performsunbalanced-balanced conversion of the signal amplified by the low noiseamplifier (LNA) 134. The mixer 133 uses the signal at the certainfrequency input from the PLL 142 to down-convert, to a baseband, thereception signal converted to a balanced signal by the balun 135. Morespecifically, the mixer 133 includes a unit that generates carrier wavesshifted by a phase of 90 degrees based on the signal at the certainfrequency input from the PLL 142. The mixer 133 uses the carrier wavesshifted by a phase of 90 degrees to perform quadrature demodulation ofthe reception signal converted by the balun 135 and generates an I(In-phase) signal with the same phase as the reception signal and a Q(Quad-phase) signal with the phase delayed by 90 degrees.

The filter 132 extracts signals with desired frequency components fromthe I signal and the Q signal. Gains of the I signal and the Q signalextracted by the filter 132 are adjusted, and the I signal and the Qsignal are output from the RF IC 121. The ADC 117 in the baseband IC 111performs AD conversion of the input signal from the RF IC 121. Morespecifically, the ADC 117 converts the I signal to a digital I signaland converts the Q signal to a digital Q signal. Note that a singlesystem signal may be received without performing quadraturedemodulation.

When a plurality of antennas are provided, the number of provided ADCsmay correspond to the number of antennas. Based on the digital I signaland the digital Q signal, the baseband circuit 112 executes a process ofthe physical layer and the like, such as demodulation process, errorcorrecting code process, and process of physical header, and obtains aframe. The baseband circuit 112 applies a process of the MAC layer tothe frame. Note that the baseband circuit 112 may be configured toexecute a process of TCP/IP when the TCP/IP is implemented.

Sixth Embodiment

FIG. 28 is a functional block diagram of the terminal (STA) 500according to a sixth embodiment. The STA 500 includes a communicationprocessor 501, a transmitter 502, a receiver 503, an antenna 51A, anapplication processor 504 a memory 505, and a second wirelesscommunication module 506. The base station (AP) may have the similarconfiguration.

The communication processor 501 has the functions similar to MAC/PHYmanager as described in the first embodiment. The transmitter 502 andthe receiver 503 have the functions similar to PHY processor and MACprocessor as described in the first embodiment. The transmitter 502 andthe receiver 503 may perform analog domain processing in PHY processorand the communication processor 501 may perform digital domainprocessing in MAC processor and digital domain processing in PHYprocessor. The communication processor 501 may internally possess abuffer for transferring data to and from the application processor 504.The buffer may be a volatile memory, such as an SRAM or a DRAM, or maybe a non-volatile memory, such as a NAND or an MRAM.

The application processor 504 performs wireless communication throughthe communication processor 501, data writing or reading with the memory505 and wireless communication through the second wireless communicationmodule 506. The application processor 504 performs various processingsuch as Web browsing or multimedia processing of video or music or thelike. The operation of application processor 504 may be carried out bysoftware (program) processing by a processor such as CPU, by hardware,or both of them.

The memory 505 saves data received at the receiver 503 or the secondwireless communication module 506, or data processed by the applicationprocessor 504. The memory 505 may be a volatile memory such as a DRAM ormay be a non-volatile memory, such as a NAND or an MRAM. The memory 505may be an SSD, an HDD, an SD card, or an eMMC or the like. The memory505 may be arranged out of the access point 500.

The second wireless communication module 506 has the similarconfiguration to the WLAN module as shown in FIG. 26 or FIG. 27 as oneexample. The second wireless communication module 506 performs wirelesscommunication in a different manner than that realized by thecommunication processor 501, the transmitter 502 and the receiver 503.For example, in a case that the communication processor 501, thetransmitter 502 and the receiver 503 perform wireless communication incompliance with IEEE802.11 standard, the second wireless communicationmodule 506 may perform wireless communication in compliance with anotherwireless communication standard such as Bluetooth (trademark), LTE,Wireless HD or the like. The communication processor 501, thetransmitter 502, the receiver 503 may perform wireless communication at2.4 GHz/5 GHz and the second wireless communication module 506 mayperform wireless communication at 60 GHz.

In the embodiment, one antenna is arranged and shared by the transmitter502, the receiver 503 and the second wireless communication module 506.A switch controlling for connection destination of the antenna 51A maybe arranged and thereby the antenna may be shared. A plurality ofantennas may be arranged and may be employed by the transmitter 502, thereceiver 503, and the second wireless communication module 506,respectively.

As one example, the communication processor 501 corresponds to anintegrated circuit, and the transmitter 502 and the receiver 503corresponds to an RF integrated circuit which transmits and receivesframes. A set of the communication processor 501 and the applicationprocessor 504 is configured by one integrated circuit (1 chip). A partof the second wireless communication module 506 and the applicationprocessor 504 may be configured by one integrated circuit (1 chip).

The application processor performs control of wireless communicationthrough the communication processor 501 and wireless communicationthrough the second wireless communication module 506.

Seventh Embodiment

FIG. 29A and FIG. 29B are perspective views of wireless terminalaccording to the present embodiment. The wireless terminal in FIG. 29Ais a notebook PC 301 and the wireless communication device (or awireless device) in FIG. 29B is a mobile terminal 321. Each of themcorresponds to one form of a terminal (which may indicate a basestation). The notebook PC 301 and the mobile terminal 321 are equippedwith wireless communication devices 305 and 315, respectively. Thewireless communication device provided in a terminal (which may indicatea base station) which has been described above can be used as thewireless communication devices 305 and 315. A wireless terminal carryinga wireless communication device is not limited to notebook PCs andmobile terminals. For example, it can be installed in a TV, a digitalcamera, a wearable device, a tablet, a smart phone, a gaming device, anetwork storage device, a monitor, a digital audio player, a web camera,a video camera, a projector, a navigation system, an external adapter,an internal adapter, a set top box, a gateway, a printer server, amobile access point, a router, an enterprise/service provider accesspoint, a portable device, a handheld device, a vehicle and so on.

Moreover, a wireless communication device installed in a terminal (whichmay indicate a base station) can also be provided in a memory card. FIG.30 illustrates an example of a wireless communication device mounted ona memory card. A memory card 331 contains a wireless communicationdevice 355 and a body case 332. The memory card 331 uses the wirelesscommunication device 355 for wireless communication with externaldevices. Here, in FIG. 30, the description of other installed elements(for example, a memory, and so on) in the memory card 331 is omitted.

Eighth Embodiment

In the present embodiment, a bus, a processor unit and an externalinterface unit are provided in addition to the configuration of thewireless communication device (the wireless communication device of theterminal (which may indicate the base station)) according to any of theabove embodiments. The processor unit and the external interface unitare connected with an external memory (a buffer) through the bus. Afirmware operates the processor unit. Thus, by adopting a configurationin which the firmware is included in the wireless communication device,the functions of the wireless communication device can be easily changedby rewriting the firmware. The processing unit in which the firmwareoperates may be a processor that performs the process of thecommunication controlling device or the control unit according to thepresent embodiment, or may be another processor that performs a processrelating to extending or altering the functions of the process of thecommunication controlling device or the control unit. The processingunit in which the firmware operates may be included in the access pointor the wireless terminal according to the present embodiment.Alternatively, the processing unit may be included in the integratedcircuit of the wireless communication device installed in the accesspoint, or in the integrated circuit of the wireless communication deviceinstalled in the wireless terminal.

Ninth Embodiment

In the present embodiment, a clock generating unit is provided inaddition to the configuration of the wireless communication device (thewireless communication device of the terminal (which may indicate thebase station)) according to any of the above embodiments. The clockgenerating unit generates a clock and outputs the clock from an outputterminal to the exterior of the wireless communication device. Thus, byoutputting to the exterior the clock generated inside the wirelesscommunication device and operating the host by the clock output to theexterior, it is possible to operate the host and the wirelesscommunication device in a synchronized manner.

Tenth Embodiment

In the present embodiment, a power source unit, a power sourcecontrolling unit and a wireless power feeding unit are included inaddition to the configuration of the wireless communication device (thewireless communication device of the terminal (which may indicate thebase station)) according to any of the above embodiments. The powersupply controlling unit is connected to the power source unit and to thewireless power feeding unit, and performs control to select a powersource to be supplied to the wireless communication device. Thus, byadopting a configuration in which the power source is included in thewireless communication device, power consumption reduction operationsthat control the power source are possible.

Eleventh Embodiment

In the present embodiment, a SIM card is added to the configuration ofthe wireless communication device according to any of the aboveembodiments. For example, the SIM card is connected with the controller,the transmitter, the receiver or plural of them in the wirelesscommunication device. Thus, by adopting a configuration in which the SIMcard is included in the wireless communication device, authenticationprocessing can be easily performed.

Twelfth Embodiment

In the eighth embodiment, a video image compressing/decompressing unitis added to the configuration of the wireless communication deviceaccording to any of the above embodiments. The video imagecompressing/decompressing unit is connected to the bus. Thus, byadopting a configuration in which the video imagecompressing/decompressing unit is included in the wireless communicationdevice, transmitting a compressed video image and decompressing areceived compressed video image can be easily done.

Thirteenth Embodiment

In the present embodiment, an LED unit is added to the configuration ofthe wireless communication device (the wireless communication device ofthe terminal (which may indicate the base station)) according to any ofthe above embodiments. For example, the LED unit is connected to thecontroller, the transmitter, the receiver or plural of them in thewireless communication device. Thus, by adopting a configuration inwhich the LED unit is included in the wireless communication device,notifying the operation state of the wireless communication device tothe user can be easily done.

Fourteenth Embodiment

In the present embodiment, a vibrator unit is included in addition tothe configuration of the wireless communication device wirelesscommunication device (the wireless communication device of the terminal(which may indicate the base station)) according to any of the aboveembodiments. For example, the vibrator unit is connected to at least oneof the controller, the transmitter, the receiver or plural of them inthe wireless communication device. Thus, by adopting a configuration inwhich the vibrator unit is included in the wireless communicationdevice, notifying the operation state of the wireless communicationdevice to the user can be easily done.

Fifteenth Embodiment

In the present embodiment, the configuration of the wirelesscommunication device includes a display in addition to the configurationof the wireless communication device (the wireless communication deviceof the terminal (which may indicate the base station)) according to anyone of the above embodiments. The display may be connected to thecontroller, the transmitter, the receiver or plural of them in thewireless communication device via a bus (not shown). As seen from theabove, the configuration including the display to display the operationstate of the wireless communication device on the display allows theoperation status of the wireless communication device to be easilynotified to a user.

Sixteenth Embodiment

In the present embodiment, [1] the frame type in the wirelesscommunication system, [2] a technique of disconnection between wirelesscommunication devices, [3] an access scheme of a wireless LAN system and[4] a frame interval of a wireless LAN are described.

[1] Frame Type in Communication System

Generally, as mentioned above, frames treated on a wireless accessprotocol in a wireless communication system are roughly divided intothree types of the data frame, the management frame and the controlframe. These types are normally shown in a header part which is commonlyprovided to frames. As a display method of the frame type, three typesmay be distinguished in one field or may be distinguished by acombination of two fields. In IEEE 802.11 standard, identification of aframe type is made based on two fields of Type and Subtype in the FrameControl field in the header part of the MAC frame. The Type field is onefor generally classifying frames into a data frame, a management frame,or a control frame and the Subtype field is one for identifying moredetailed type in each of the classified frame types such as a beaconframe belonging to the management frame.

The management frame is a frame used to manage a physical communicationlink with a different wireless communication device. For example, thereare a frame used to perform communication setting with the differentwireless communication device or a frame to release communication link(that is, to disconnect the connection), and a frame related to thepower save operation in the wireless communication device.

The data frame is a frame to transmit data generated in the wirelesscommunication device to the different wireless communication deviceafter a physical communication link with the different wirelesscommunication device is established. The data is generated in a higherlayer of the present embodiment and generated by, for example, a user'soperation.

The control frame is a frame used to perform control at the time oftransmission and reception (exchange) of the data frame with thedifferent wireless communication device. A response frame transmittedfor the acknowledgment in a case where the wireless communication devicereceives the data frame or the management frame, belongs to the controlframe. The response frame is, for example, an ACK frame or a BlockACKframe. The RTS frame and the CTS frame are also the control frame.

These three types of frames are subjected to processing based on thenecessity in the physical layer and then transmitted as physical packetsvia an antenna. In IEEE 802.11 standard (including the extended standardsuch as IEEE Std 802.11ac-2013), an association process is defined asone procedure for connection establishment. The association requestframe and the association response frame which are used in the procedureare a management frame. Since the association request frame and theassociation response frame is the management frame transmitted in aunicast scheme, the frames causes the wireless communication terminal inthe receiving side to transmit an ACK frame being a response frame. TheACK frame is a control frame as described in the above.

[2] Technique of Disconnection Between Wireless Communication Devices

For disconnection of the connection (release), there are an explicittechnique and an implicit technique. As the explicit technique, a frameto disconnect any one of the connected wireless communication devices istransmitted. This frame corresponds to Deauthentication frame defined inIEEE 802.11 standard and is classified into the management frame.Normally, it is determined that the connection is disconnected at thetiming of transmitting the frame to disconnect the connection in awireless communication device on the side to transmit the frame and atthe timing of receiving the frame to disconnect the connection in awireless communication device on the side to receive the frame.Afterward, it returns to the initial state in a communication phase, forexample, a state to search for a wireless communication device of thecommunicating partner. In a case that the wireless communication basestation disconnects with a wireless communication terminal, for example,the base station deletes information on the wireless communicationdevice from a connection management table if the base station holds theconnection management table for managing wireless communicationterminals which entries into the BSS of the base station-self. Forexample, in a case that the base station assigns an AID to each wirelesscommunication terminal which entries into the BSS at the time when thebase station permitted each wireless communication terminal to connectto the base station-self in the association process, the base stationdeletes the held information related to the AID of the wirelesscommunication terminal disconnected with the base station and mayrelease the AID to assign it to another wireless communication devicewhich newly entries into the BSS.

On the other hand, as the implicit technique, it is determined that theconnection state is disconnected in a case where frame transmission(transmission of a data frame and management frame or transmission of aresponse frame with respect to a frame transmitted by the subjectdevice) is not detected from a wireless communication device of theconnection partner which has established the connection for a certainperiod. Such a technique is provided because, in a state where it isdetermined that the connection is disconnected as mentioned above, astate is considered where the physical wireless link cannot be secured,for example, the communication distance to the wireless communicationdevice of the connection destination is separated and the radio signalscannot be received or decoded. That is, it is because the reception ofthe frame to disconnect the connection cannot be expected.

As a specific example to determine the disconnection of connection in animplicit method, a timer is used. For example, at the time oftransmitting a data frame that requests an acknowledgment responseframe, a first timer (for example, a retransmission timer for a dataframe) that limits the retransmission period of the frame is activated,and, if the acknowledgement response frame to the frame is not receiveduntil the expiration of the first timer (that is, until a desiredretransmission period passes), retransmission is performed. When theacknowledgment response frame to the frame is received, the first timeris stopped.

On the other hand, when the acknowledgment response frame is notreceived and the first timer expires, for example, a management frame toconfirm whether a wireless communication device of a connection partneris still present (in a communication range) (in other words, whether awireless link is secured) is transmitted, and, at the same time, asecond timer (for example, a retransmission timer for the managementframe) to limit the retransmission period of the frame is activated.Similarly to the first timer, even in the second timer, retransmissionis performed if an acknowledgment response frame to the frame is notreceived until the second timer expires, and it is determined that theconnection is disconnected when the second timer expires.

Alternatively, a third timer is activated when a frame is received froma wireless communication device of the connection partner, the thirdtimer is stopped every time the frame is newly received from thewireless communication device of the connection partner, and it isactivated from the initial value again. When the third timer expires,similarly to the above, a management frame to confirm whether thewireless communication device of the connection party is still present(in a communication range) (in other words, whether a wireless link issecured) is transmitted, and, at the same time, a second timer (forexample, a retransmission timer for the management frame) to limit theretransmission period of the frame is activated. Even in this case,retransmission is performed if an acknowledgment response frame to theframe is not received until the second timer expires, and it isdetermined that the connection is disconnected when the second timerexpires. The latter management frame to confirm whether the wirelesscommunication device of the connection partner is still present maydiffer from the management frame in the former case. Moreover, regardingthe timer to limit the retransmission of the management frame in thelatter case, although the same one as that in the former case is used asthe second timer, a different timer may be used.

[3] Access Scheme of Wireless LAN System

For example, there is a wireless LAN system with an assumption ofcommunication or competition with a plurality of wireless communicationdevices. CSMA/CA is set as the basis of an access scheme in IEEE802.11(including an extension standard or the like) wireless LAN. In a schemein which transmission by a certain wireless communication device isgrasped and transmission is performed after a fixed time from thetransmission end, simultaneous transmission is performed in theplurality of wireless communication devices that grasp the transmissionby the wireless communication device, and, as a result, radio signalscollide and frame transmission fails. By grasping the transmission bythe certain wireless communication device and waiting for a random timefrom the transmission end, transmission by the plurality of wirelesscommunication devices that grasp the transmission by the wirelesscommunication device stochastically disperses. Therefore, if the numberof wireless communication devices in which the earliest time in a randomtime is subtracted is one, frame transmission by the wirelesscommunication device succeeds and it is possible to prevent framecollision. Since the acquisition of the transmission right based on therandom value becomes impartial between the plurality of wirelesscommunication devices, it can say that a scheme adopting CollisionAvoidance is a suitable scheme to share a radio medium between theplurality of wireless communication devices.

[4] Frame Interval of Wireless LAN

The frame interval of IEEE802.11 wireless LAN is described. There areseveral types of frame intervals used in IEEE802.11 wireless LAN, suchas distributed coordination function interframe space (DIFS),arbitration interframe space (AIFS), point coordination functioninterframe space (PIFS), short interframe space (SIFS), extendedinterframe space (EIFS) and reduced interframe space (RIFS).

The definition of the frame interval is defined as a continuous periodthat should confirm and open the carrier sensing idle beforetransmission in IEEE802.11 wireless LAN, and a strict period from aprevious frame is not discussed. Therefore, the definition is followedin the explanation of IEEE802.11 wireless LAN system. In IEEE802.11wireless LAN, a waiting time at the time of random access based onCSMA/CA is assumed to be the sum of a fixed time and a random time, andit can say that such a definition is made to clarify the fixed time.

DIFS and AIFS are frame intervals used when trying the frame exchangestart in a contention period that competes with other wirelesscommunication devices on the basis of CSMA/CA. DIFS is used in a casewhere priority according to the traffic type is not distinguished, AIFSis used in a case where priority by traffic identifier (TID) isprovided.

Since operation is similar between DIFS and AIFS, an explanation belowwill mainly use AIFS. In IEEE802.11 wireless LAN, access controlincluding the start of frame exchange in the MAC layer is performed. Inaddition, in a case where QoS (Quality of Service) is supported whendata is transferred from a higher layer, the traffic type is notifiedtogether with the data, and the data is classified for the priority atthe time of access on the basis of the traffic type. The class at thetime of this access is referred to as “access category (AC)”. Therefore,the value of AIFS is provided every access category.

PIFS denotes a frame interval to enable access which is morepreferential than other competing wireless communication devices, andthe period is shorter than the values of DIFS and AIFS. SIFS denotes aframe interval which can be used in a case where frame exchangecontinues in a burst manner at the time of transmission of a controlframe of a response system or after the access right is acquired once.EIFS denotes a frame interval caused when frame reception fails (whenthe received frame is determined to be error).

RIFS denotes a frame interval which can be used in a case where aplurality of frames are consecutively transmitted to the same wirelesscommunication device in a burst manner after the access right isacquired once, and a response frame from a wireless communication deviceof the transmission partner is not requested while RIFS is used.

Here, FIG. 31 illustrates one example of frame exchange in a competitiveperiod based on the random access in IEEE802.11 wireless LAN.

When a transmission request of a data frame (W_DATA1) is generated in acertain wireless communication device, a case is assumed where it isrecognized that a medium is busy (busy medium) as a result of carriersensing. In this case, AIFS of a fixed time is set from the time pointat which the carrier sensing becomes idle, and, when a random time(random backoff) is set afterward, data frame W_DATA1 is transmitted tothe communicating partner.

The random time is acquired by multiplying a slot time by a pseudorandominteger led from uniform distribution between contention windows (CW)given by integers from 0. Here, what multiplies CW by the slot time isreferred to as “CW time width”. The initial value of CW is given byCWmin, and the value of CW is increased up to CWmax everyretransmission. Similarly to AIFS, both CWmin and CWmax have valuesevery access category. In a wireless communication device oftransmission destination of W_DATA1, when reception of the data framesucceeds, a response frame (W_ACK1) is transmitted after SIFS from thereception end time point. If it is within a transmission burst timelimit when W_ACK1 is received, the wireless communication device thattransmits W_DATA1 can transmit the next frame (for example, W_DATA2)after SIFS.

Although AIFS, DIFS, PIFS and EIFS are functions between SIFS and theslot-time, SIFS and the slot time are defined every physical layer.Moreover, although parameters whose values being set according to eachaccess category, such as AIFS, CWmin and CWmax, can be set independentlyby a communication group (which is a basic service set (BSS) inIEEE802.11 wireless LAN), the default values are defined.

For example, in the definition of 802.11ac, with an assumption that SIFSis 16 μs and the slot time is 9 μs, and thereby PIFS is 25 μs, DIFS is34 μs, the default value of the frame interval of an access category ofBACKGROUND (AC_BK) in AIFS is 79 μs, the default value of the frameinterval of BEST EFFORT (AC_BE) is 43 μs, the default value of the frameinterval between VIDEO(AC_VI) and VOICE(AC_VO) is 34 μs, and the defaultvalues of CWmin and CWmax are 31 and 1023 in AC_BK and AC_BE, 15 and 31in AC_VI and 7 and 15 in AC_VO. Here, EIFS denotes the sum of SIFS,DIFS, and the time length of a response frame transmitted at the lowestmandatory physical rate. In the wireless communication device which caneffectively takes EIFS, it may estimate an occupation time length of aPHY packet conveying a response frame directed to a PHY packet due towhich the EIFS is caused and calculates a sum of SIFS, DIFS and theestimated time to take the EIFS. Note that the frames described in theembodiments may indicate not only things called frames in, for example,IEEE 802.11 standard, but also things called packets, such as Null DataPackets.

The terms used in each embodiment should be interpreted broadly. Forexample, the term “processor” may encompass a general purpose processor,a central processing unit (CPU), a microprocessor, a digital signalprocessor (DSP), a controller, a microcontroller, a state machine, andso on. According to circumstances, a “processor” may refer to anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), and a programmable logic device (PLD), etc. The term“processor” may refer to a combination of processing devices such as aplurality of microprocessors, a combination of a DSP and amicroprocessor, or one or more microprocessors in conjunction with a DSPcore.

As another example, the term “memory” may encompass any electroniccomponent which can store electronic information. The “memory” may referto various types of media such as a random access memory (RAM), aread-only memory (ROM), a programmable read-only memory (PROM), anerasable programmable read only memory (EPROM), an electrically erasablePROM (EEPROM), a non-volatile random access memory (NVRAM), a flashmemory, and a magnetic or optical data storage, which are readable by aprocessor. It can be said that the memory electronically communicateswith a processor if the processor read and/or write information for thememory.

The memory may be arranged within a processor and also in this case, itcan be said that the memory electronically communication with theprocessor. The circuitry” may refer one or more electric circuitsdisposed on a single chip, or may refer one or more electric circuitsdisposed on a plurality of chips or a plurality of devices in adispersed manner.

In the specification, the expression “at least one of a, b or c” is anexpression to encompass not only “a”, “b”, “c”, “a and b”, “a and c”, “band c”, “a, b and c” or any combination thereof but also a combinationof at least a plurality of same elements such as “a and a”, “a, b and b”or “a, a, b, b, c and c”. Also, the expression is an expression to allowa set including an element other than “a”, “b” and “c” such as “a, b, c,and d”.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions.

1.-17. (canceled)
 18. A wireless communication device communicating witha second wireless communication device, comprising: a receiverconfigured to receive a terminal identifier of a first terminal being atarget for downlink frequency multiplexing transmission from the secondwireless communication device, the first terminal existing at a neighborarea of the second wireless communication device and the terminalidentifier of the first terminal being allocated by the second wirelesscommunication device, and receive information identifying, among aplurality of frequency components, a first frequency component allocatedto the first terminal; a controller configured to select, among aplurality of second terminals belonging to the wireless communicationdevice, a second terminal existing at a neighbor area of the wirelesscommunication device, a terminal identifier of the second terminal beingallocated by the wireless communication device and being same as theterminal identifier of the first terminal, and allocate the firstfrequency component to the selected second terminal; and a transmitterconfigured to transmit a first physical packet in a period at leastpartially overlapping with a period in which a second physical packet istransmitted from the second wireless communication device, the firstphysical packet including (1) a first header containing a plurality offirst fields associated with the plurality of frequency components, theterminal identifier of the selected second terminal being set in a fieldcorresponding to the first frequency component among the plurality offirst fields, and (2) a first frame addressed to the second terminal,wherein the first header is transmitted at a frequency band includingthe plurality of frequency components and the first frame is transmittedvia the first frequency component, the transmitter being configured totransmit the terminal identifier of the second terminal and theinformation identifying the first frequency component to the secondwireless communication device, wherein the second physical packetincluding (1) a second header containing a plurality of second fieldsassociated with the plurality of frequency components, the terminalidentifier of the first terminal being set in a field corresponding tothe first frequency component among the plurality of second fields, and(2) a second frame addressed to the first terminal, the second headerbeing transmitted at the frequency band including the plurality offrequency components and the second frame is transmitted via the firstfrequency component, and a format of the first header being the same asa format of the second header.
 19. The wireless communication deviceaccording to claim 18, wherein the receiver is configured to receivetiming information of transmission of the second physical packet fromthe second wireless communication device, and the transmitter isconfigured to transmit the first physical packet in accordance with thetiming information.
 20. The wireless communication device according toclaim 18, wherein the receiver is configured to receive a terminalidentifier of another first terminal being a target for the downlinkfrequency multiplexing transmission from the second wirelesscommunication device, the terminal identifier of the another firstterminal being allocated by the second wireless communication device,the another first terminal existing in a distant area of the secondwireless communication device and receiving information identifying asecond frequency component allocated to the another first terminal, thecontroller is configured to allocate the second frequency component tonone of a plurality of second terminals, and the transmitter isconfigured to set the terminal identifier of the another first terminalin a field corresponding to the second frequency component among theplurality of first fields, in the first header, the terminal identifierof the another first terminal being set in a field corresponding to thesecond frequency component among the plurality of second fields, in thesecond header of the second physical packet.
 21. The wirelesscommunication system according to claim 20, wherein the controller isconfigured to select, among the plurality of second terminals, anothersecond terminal other than the second terminal allocated with the firstfrequency component, the another second terminal existing in a distantarea of the wireless communication device and is configured to allocatea third frequency component to the other second terminal, and thetransmitter is configured to set a terminal identifier of the othersecond terminal in a field corresponding to the third frequencycomponent among the plurality of first fields in the first header, theterminal identifier of the another second terminal being allocated bythe wireless communication device, and the transmitter is configuredtransmit the terminal identifier of the another second terminal andinformation to specify the third frequency component to the secondwireless communication device, the terminal identifier of the anothersecond terminal being set in a field corresponding to the thirdfrequency component among the plurality of second fields, in the secondheader of the second physical packet.
 22. The wireless communicationsystem according to claim 18, comprising at least one antenna.
 23. Awireless communication device communicating with a second wirelesscommunication device, comprising: a receiver configured to receive aterminal identifier of a first terminal being a target for downlinkfrequency multiplexing transmission from second wireless communicationdevice, and receive information identifying, among a plurality offrequency components, a first frequency component allocated to the firstterminal, the first terminal existing at a neighbor area of the secondwireless communication device and the terminal identifier of the firstterminal being allocated by the second wireless communication device; acontroller configured to select, among a plurality second terminalsbelonging to the wireless communication device, at least one secondterminal allocated with the first frequency component, the at least onesecond terminal existing at a neighbor area of the wirelesscommunication device and the terminal identifier of the at least onesecond terminal being allocated by the wireless communication device;and a transmitter configured to transmit a first physical packet in aperiod at least partially overlapping with a period in which a secondphysical packet is transmitted from the second wireless communicationdevice, the first physical packet including (1) a first headercontaining at least a plurality of first fields associated with thefirst frequency component, the terminal identifier of the first terminalbeing set in a field of the plurality of first fields associated withthe first frequency component, a terminal identifier of the at least oneselected second terminal being set in at least one field of theplurality of first fields associated with the first frequency component,and (2) at least one first frame addressed to the at least one secondterminal, wherein the first header is transmitted at a frequency bandincluding the plurality of frequency components and the at least onefirst frame is transmitted via the first frequency component in aspatial multiplexing manner, the transmitter is configured to transmitthe terminal identifier of the at least one second terminal and theinformation identifying the first frequency component to the secondwireless communication device, the second physical packet includes (1) asecond header containing a plurality of second fields associated withthe first frequency component, the terminal identifier of the firstterminal being set in a field of the plurality of second fieldsassociated with the first frequency component and the terminalidentifier of the at least one selected second terminal being set in atleast one field of the plurality of second fields associated with thefirst frequency component, and (2) a second frame addressed to the firstterminal, wherein the second header is transmitted at the frequency bandincluding the plurality of frequency components, the first frame istransmitted via the first frequency component in a spatial multiplexingmanner, and a format of the first header is the same as a format of thesecond header.
 24. The wireless communication device according to claim23, wherein the receiver is configured to receive timing information oftransmission of the second physical packet from the second wirelesscommunication device, and the transmitter is configured to transmit thesecond physical packet in accordance with the timing information. 25.The wireless communication device according to claim 23, wherein thereceiver is configured to receive a terminal identifier of another firstterminal being a target for the downlink frequency multiplexingtransmission from the second wireless communication device, andinformation identifying a second frequency component allocated to theanother first terminal, the terminal identifier of the another firstterminal being allocated by the second wireless communication device,the another first terminal existing in a distant area of the secondwireless communication device and the transmitter is configured to setthe terminal identifier of the another first terminal in a fieldcorresponding to the second frequency component, in the first header,the terminal identifier of the another first terminal being set in afield corresponding to the second frequency component, in the secondheader of the second physical packet, the second physical packetincluding a fourth frame addressed to the another first terminal, andthe fourth frame being transmitted via the second frequency component.26. The wireless communication system according to claim 25, wherein thecontroller is configured to select, among the plurality of secondterminals, another second terminal other than the at least one secondterminal among the plurality of second terminals, the another secondterminal existing in a distant area of the wireless communication deviceand being configured to determine a third frequency component allocatedto the another second terminal, and the transmitter is configured to seta terminal identifier of the another second terminal in a fieldcorresponding to the third frequency component, in the first header, thefirst physical packet includes a third frame addressed to the thirdterminal, and the transmitter is configured to transmit the third frameaddressed to the third terminal, the terminal identifier of the anothersecond terminal being set in a fourth filed corresponding to the thirdfrequency component, in the second header of the second physical packet.27. The wireless communication system according to claim 23, furthercomprising at least one antenna.
 28. A wireless communication devicecommunicating with a second wireless communication device, a receiverconfigured to receive terminal identifiers of a plurality of firstterminals being targets for uplink frequency multiplexing transmissionfrom second wireless communication device, and configured to receiveinformation identifying, among a plurality of frequency components, aplurality of first frequency components allocated to the plurality offirst terminals, the first frequency components being different fromeach other; a controller configured to determine a plurality of secondfrequency components allocated to a plurality of second terminals beingtargets for the uplink frequency multiplexing transmission, the secondfrequency components being different from each other; and a transmitterconfigured to transmit a first frame in a period at least partiallyoverlapping with a period in which a second frame is transmitted fromthe second wireless communication device, the first frame instructingthe uplink frequency multiplexing transmission, wherein the first frameincludes the terminal identifiers of the plurality of first terminalswhich are set in a plurality of first fields corresponding to theplurality of first frequency components, and terminal identifiers of theplurality of second terminals which are set in a plurality of firstfields corresponding to the plurality of second frequency components,and wherein a transmitter address of the first frame is an address ofthe second wireless communication device, and the second terminals areable to receive and interpret the first frame whose transmitter addressis the address of the second wireless communication device, wherein thesecond wireless communication device is configured to transmit a secondframe, the second frame including the terminal identifiers of theplurality of first terminals which are set in a plurality of secondfields corresponding to the plurality of first frequency components, andterminal identifiers of the plurality of second terminals which are setin a plurality of second fields corresponding to the plurality of secondfrequency components.
 29. The wireless communication device according toclaim 28, further comprising at least one antenna.
 30. A wirelesscommunication device communicating with a second wireless communicationdevice, comprising: a receiver configured to receive information of asecond frequency band used for transmission of a first frame by thesecond wireless communication device, the first frame instructing aplurality of first terminals to perform uplink frequency multiplexingtransmission at a first frequency band including a plurality offrequency components, and specifying frequency components for the uplinkfrequency multiplexing transmission to the first terminals, atransmitter configured to transmit a second frame at a third frequencyband different from the second frequency band, the second frameinstructing a plurality of second terminals belonging to the wirelesscommunication device to perform the uplink frequency multiplexingtransmission at the first frequency band and the second frame specifyingfrequency components for the uplink frequency multiplexing transmissionto the second terminals, the second frame being transmitted in a periodat least overlapping with a period in which the first frame istransmitted, a frequency component specified for a first terminalexisting in a distant area of the second wireless communication deviceis different from a frequency component specified for a second terminalin a distant area of the wireless communication device, and a frequencycomponent specified for another first terminal existing in a neighborarea of the second wireless communication device is the same as afrequency component specified for another second terminal in a neighborarea of the wireless communication device.
 31. The wirelesscommunication system according to claim 30, further comprising at leastone antenna.